Support the following packed BCD builtins for PowerPC.
  
```
__builtin_national2packed - Conversion of National format to Packed decimal format.
__builtin_packed2national - Conversion of Packed decimal format to national format.
__builtin_packed2zoned    - Conversion of Packed decimal format to Zoned decimal format.
__builtin_zoned2packed    - Conversion of Zoned decimal format to Packed decimal format.
```
### Prototypes: 
`vector unsigned char __builtin_national2packed(vector unsigned char a,
unsigned char b);`
`vector unsigned char __builtin_packed2zoned(vector unsigned char,
unsigned char);`
`vector unsigned char __builtin_zoned2packed(vector unsigned char,
unsigned char);`

The condition for the 2nd parameter is consistent over all the 3
prototypes (0 or 1 only).

`vector unsigned char __builtin_packed2national(vector unsigned char);`

Co-authored-by: himadhith <himadhith.v@ibm.com>
Co-authored-by: Tony Varghese <tonypalampalliyil@gmail.com>

Define the __dmr1024 type used to manipulate the new DMR registers
introduced by the Dense Math Facility (DMF) on PowerPC, and add six
Clang builtins that correspond to the integer outer-product accumulate
to ACC PowerPC instructions:
*  __builtin_mma_dmxvi8gerx4
* __builtin_mma_pmdmxvi8gerx4
*  __builtin_mma_dmxvi8gerx4pp
*  __builtin_mma_pmdmxvi8gerx4pp
*  __builtin_mma_dmxvi8gerx4spp
* __builtin_mma_pmdmxvi8gerx4spp.

Fixes https://github.com/llvm/llvm-project/issues/140149

Update test in prep for IR changes that will be introduced in
https://github.com/llvm/llvm-project/pull/129923

This PR removes the old `nocapture` attribute, replacing it with the new
`captures` attribute introduced in #116990. This change is
intended to be essentially NFC, replacing existing uses of `nocapture`
with `captures(none)` without adding any new analysis capabilities.
Making use of non-`none` values is left for a followup.

Some notes:
* `nocapture` will be upgraded to `captures(none)` by the bitcode
   reader.
* `nocapture` will also be upgraded by the textual IR reader. This is to
   make it easier to use old IR files and somewhat reduce the test churn in
   this PR.
* Helper APIs like `doesNotCapture()` will check for `captures(none)`.
* MLIR import will convert `captures(none)` into an `llvm.nocapture`
   attribute. The representation in the LLVM IR dialect should be updated
   separately.

If the gep is nusw (usually via inbounds) and the offset is
non-negative, we can infer nuw.

Proof: https://alive2.llvm.org/ce/z/ihztLy

See
https://discourse.llvm.org/t/cant-cannot-can-not-in-diagnostic-messages/83171

This will fix the following failure seeing on z/OS:

```
In file included from clang/test/CodeGen/PowerPC/ppc-xmmintrin.c:31:
In file included from build/lib/clang/20/include/ppc_wrappers/xmmintrin.h:44:
In file included from build/lib/clang/20/include/altivec.h:48:
In file included from build/bin/../include/c++/v1/stddef.h:27:
In file included from build/bin/../include/c++/v1/__config:14:
In file included from build/bin/../include/c++/v1/__configuration/abi.h:15:
In file included from build/bin/../include/c++/v1/__configuration/platform.h:35:
/usr/include/features.h:1:20: error: expected unqualified-id
    1 |                    ??=if                       ??/
      |                    ^
/usr/include/features.h:2140:20: error: expected unqualified-id
 2140 |                    ??=endif /* __features_h */
      |                    ^
```
Adding `-nostdlibinc` will not use standard system include path and it
will prevent above errors.

Fixes #107229