Rename the function to reflect its correct behavior and to be consistent
with `Module::getOrInsertFunction`. This is also in preparation of
adding a new `Intrinsic::getDeclaration` that will have behavior similar
to `Module::getFunction` (i.e, just lookup, no creation).

I was wondering why my use of createClassType was generating structure
reccords, and it turns out the code is wrong (or for some reason i don't
understand the intended use of the API).

clang itself does not use that part of the API, so this flew under the
radar.

Part 1 of fix for issue
https://github.com/llvm/llvm-project/issues/54624

Split from PR #87623. Clang front end changes to follow.

Use DICompositeType to represent the template alias, using its extraData
field as a tuple of DITemplateParameter to describe the template
parameters.

Added template-alias.ll  - Check DWARF emission.
Modified  frame-types.s  - Check llvm-symbolizer understands the DIE.

This patch renames DPLabel to DbgLabelRecord, in accordance with the
ongoing DbgRecord rename. This rename was fairly trivial, since DPLabel
isn't as widely used as DPValue and has no real conflicts in either its
full or abbreviated name. As usual, the entire replacement was done
automatically, with `s/DPLabel/DbgLabelRecord/` and `s/DPL/DLR/`.

This is the major rename patch that prior patches have built towards.
The DPValue class is being renamed to DbgVariableRecord, which reflects
the updated terminology for the "final" implementation of the RemoveDI
feature. This is a pure string substitution + clang-format patch. The
only manual component of this patch was determining where to perform
these string substitutions: `DPValue` and `DPV` are almost exclusively
used for DbgRecords, *except* for:

- llvm/lib/target, where 'DP' is used to mean double-precision, and so
appears as part of .td files and in variable names. NB: There is a
single existing use of `DPValue` here that refers to debug info, which
I've manually updated.
- llvm/tools/gold, where 'LDPV' is used as a prefix for symbol
visibility enums.

Outside of these places, I've applied several basic string
substitutions, with the intent that they only affect DbgRecord-related
identifiers; I've checked them as I went through to verify this, with
reasonable confidence that there are no unintended changes that slipped
through the cracks. The substitutions applied are all case-sensitive,
and are applied in the order shown:

```
  DPValue -> DbgVariableRecord
  DPVal -> DbgVarRec
  DPV -> DVR
```

Following the previous rename patches, it should be the case that there
are no instances of any of these strings that are meant to refer to the
general case of DbgRecords, or anything other than the DPValue class.
The idea behind this patch is therefore that pure string substitution is
correct in all cases as long as these assumptions hold.

Reland #82363 after fixing build failure
https://lab.llvm.org/buildbot/#/builders/5/builds/41428.

Memory sanitizer detects usage of `RawData` union member which is not
filled directly. Instead, the code relies on filling `Data` union
member, which is a struct consisting of signing schema parameters.

According to https://en.cppreference.com/w/cpp/language/union, this is
UB:
"It is undefined behavior to read from the member of the union that
wasn't most recently written".

Instead of relying on compiler allowing us to do dirty things, do not
use union and only store `RawData`. Particular ptrauth parameters are
obtained on demand via bit operations.

Original PR description below.

Emit `__ptrauth`-qualified types as `DIDerivedType` metadata nodes in IR
with tag `DW_TAG_LLVM_ptrauth_type`, baseType referring to the type
which has the qualifier applied, and the following parameters
representing the signing schema:

- `ptrAuthKey` (integer)
- `ptrAuthIsAddressDiscriminated` (boolean)
- `ptrAuthExtraDiscriminator` (integer)
- `ptrAuthIsaPointer` (boolean)
- `ptrAuthAuthenticatesNullValues` (boolean)

Co-authored-by: Ahmed Bougacha <ahmed@bougacha.org>

As part of the effort to rename the DbgRecord classes, this patch
renames the widely-used functions that operate on DbgRecords but refer
to DbgValues or DPValues in their names to refer to DbgRecords instead;
all such functions are defined in one of `BasicBlock.h`,
`Instruction.h`, and `DebugProgramInstruction.h`.

This patch explicitly does not change the names of any comments or
variables, except for where they use the exact name of one of the
renamed functions. The reason for this is reviewability; this patch can
be trivially examined to determine that the only changes are direct
string substitutions and any results from clang-format responding to the
changed line lengths. Future patches will cover renaming variables and
comments, and then renaming the classes themselves.

Have DIBuilder conditionally insert either debug intrinsics or DbgRecord
depending on the module's IsNewDbgInfoFormat flag. The insertion methods
now return a `DbgInstPtr` (a `PointerUnion<Instruction *, DbgRecord
*>`).

Add a unittest for both modes (I couldn't find an existing test testing
insertion behaviours specifically).

This patch changes the existing assumption that DbgRecords are only ever
inserted if there's an instruction to insert-before because clang
currently inserts debug intrinsics while CodeGening (like any other
instruction) meaning it'll try inserting to the end of a block without a
terminator. We already have machinery in place to maintain the
DbgRecords when a terminator is removed - these become "trailing
DbgRecords" which are re-attached when a new instruction is inserted.
All I've done is allow this state to occur while inserting DbgRecords
too, i.e., it's not only removing terminators that causes this valid
transient state, but inserting DbgRecords into incomplete blocks too.

The C API will be updated in follow up patches.

---

Note: this doesn't mean clang is emitting DbgRecords yet, because the
modules it creates are still always in the old debug mode. That will
come in a future patch.

Reverts llvm/llvm-project#82363

See a build failure related to an issue discovered by memory sanitizer
(use of uninitialized value):
https://lab.llvm.org/buildbot/#/builders/37/builds/31965