Relands #149701 which was reverted in
https://github.com/llvm/llvm-project/commit/185ae5cdc695248b58ae017508cc764c19bee5b7
because it broke demangling of Itanium symbols on i386.

The last commit in this PR adds the fix for this (discussed in #160930).
On x86 environments, the prefix of `__cdecl` functions will now be
removed to match DWARF. I opened #161676 to discuss this for the other
calling conventions.

This reverts commit e98f34eb08b2bf7aed787e7f8a7cea9111f044c8.

This broke demangling of Itanium symbols on i386.

Before, functions created using the NativePDB plugin would not know
about their mangled name. This showed when printing a stacktrace. There,
only the function name was shown. For
https://github.com/llvm/llvm-project/issues/143149, the mangled function
name is required to separate different parts.

This PR adds that name if available.

The Clang AST nodes also take in a mangled name, which was previously
unset. I don't think this unblocks anything further, because Clang can
mangle the function anyway.

Relands #152295.

Checking for the overloads did not account for them being out of order.
For example, [the failed
output](https://github.com/llvm/llvm-project/pull/152295#issuecomment-3177563247)
contained the overloads, but out of order. The last commit here fixes
that by using `-DAG`.

---------

Co-authored-by: Jonas Devlieghere <jonas@devlieghere.com>

Reverts llvm/llvm-project#152295

This adds the ability for functions to be matched by their basename.

Before, the globals were searched for the name. This works if the full
name is available but fails for basenames.
PDB only includes the full names of functions, so we need to cache all
basenames. This is (again) very similar to
[SymbolFilePDB](https://github.com/llvm/llvm-project/blob/b242150b075a8a720b00821682a9469258bbcd30/lldb/source/Plugins/SymbolFile/PDB/SymbolFilePDB.cpp#L1291-L1383).
There are two main differences:

- We can't just access the parent of a function to determine that it's a
member function - we need to check the type of the function, and its
"this type".
- SymbolFilePDB saved the full method name in the map. However, when
searching for methods, only the basename is passed, so the function
never found any methods.

Fixes #51933.

---------

Co-authored-by: Jonas Devlieghere <jonas@devlieghere.com>

This is a split of D113724. Calling `TypeSystemClang::AddMethodToCXXRecordType`
to create function decls for class methods.

Differential Revision: https://reviews.llvm.org/D113930

I don't see a reason why not to. If we allows lookup functions by full names,
I can change the test case in D113930 to use `lldb-test symbols --find=function --name=full::name --function-flags=full ...`,
though the duplicate method decl prolem is still there for `lldb-test symbols --dump-ast`.
That's a seprate bug, we can fix it later.

Differential Revision: https://reviews.llvm.org/D114467