Add support for specifying range attributes in Intrinsics.td. Use this
to specify the ucmp/scmp range [-1,2).

This case is trickier than existing intrinsic attributes, because we
need to create the attribute with the correct bitwidth. As such, the
attribute construction now needs to be aware of the function type.

We also need to be careful to no longer assign attributes on intrinsics
with invalid signatures, as we'd make invalid assumptions about the
number of arguments etc otherwise.

Fixes https://github.com/llvm/llvm-project/issues/130179.

Previously the check comments indicated that [pi][0-9]+ would match as a
type suffix, however the check itself was looking for [pi][0-9]* and
hence an 'i' suffix in isolation was being considered as a type suffix
despite it not having a bitwidth.

This change makes the check consistent with the comment and looks for
[pi][0-9]+

This is a part of effort to have better const correctness in TableGen
backends:


https://discourse.llvm.org/t/psa-planned-changes-to-tablegen-getallderiveddefinitions-api-potential-downstream-breakages/81089

Check name conflicts between intrinsics caused by mangling suffix.

If the base name of an overloaded intrinsic is a proper prefix of
another intrinsic, check if the other intrinsic name suffix after the
proper prefix can match a mangled type and issue an error if it can.

Change `CodeGenIntrinsics` classes to vend out const references to
`CodeGenIntrinsic` or `TargetSet` objects.

Validate that for target independent intrinsics the second dotted
component of their name (after the `llvm.`) does not match any existing
target names (for which atleast one intrinsic has been defined). Doing
so is invalid as LLVM will search for that intrinsic in that target's
intrinsic table and not find it, and conclude that its an unknown
intrinsic.

Speed up sorting of intrinsics by using the TargetPrefix to only
discriminate beteween target dependent vs target independent intrinsics
where target independent ones need to be sorted before target dependent
ones. When comparing two target dependent intrinsics, the Name already
includes `llvm.<TargetPrefix>` as a prefix, so no need to needlessly
compare it separately.

Check for duplicate intrinsic names in the intrinsic emitter backend and
issue a fatal error if we find one.

Split RecordKeeper `getAllDerivedDefinitions` family of functions into
two variants:
  (a) non-const ones that return vectors of `Record *` and 
  (b) const ones, that return vector/ArrayRef of `const Record *`.

This will help gradual migration of TableGen backends to use 
`const RecordKeeper` and by implication change code to work 
with const pointers and better const correctness.

Existing backends are not yet compatible with the const family of
functions, so change them to use a non-constant `RecordKeeper` 
reference, till they are migrated.