Backport bee4bd7 and bfb1a33 to 14.0.0

[AnastasiaStulova]

These patches are required for the OpenCL 3.0 completion and they are not affecting widespread functionality as they are specific to OpenCL (committed by @azabazno).

bee4bd7 - [OpenCL] Add support of language builtins for OpenCL C 3.0
bfb1a33 - [OpenCL] Adjust diagnostic for subgroup support.

Due to dependency, they are grouped together.

[llvmbot]

@llvm/issue-subscribers-opencl

[AnastasiaStulova]

Unfortunately, this patch doesn't apply cleanly to the release branch:
#53763 (comment)

[AnastasiaStulova]

/cherry-pick bfb1a33

[llvmbot]

Failed to cherry-pick: bfb1a33

https://github.com/llvm/llvm-project/actions/runs/1840894853

Please manually backport the fix and push it to your github fork. Once this is done, please add a comment like this:

/branch <user>/<repo>/<branch>

[AnastasiaStulova]

/cherry-pick bee4bd7 bfb1a33

[llvmbot]

/branch llvmbot/llvm-project/issue53823

[llvmbot]

/pull-request llvmbot#56