[clang][x86][bytecode] Replace interp__builtin_parity/clrsb/bitreverse/ffs with static bool interp__builtin_elementwise_int_unaryop callback

[RKSimon]

Once #160280 has landed all of these functions can be replaced with simple interp__builtin_elementwise_int_unaryop callbacks

interp__builtin_parity
interp__builtin_clrsb
interp__builtin_bitreverse
interp__builtin_ffs

[llvmbot]

@llvm/issue-subscribers-backend-x86

Author: Simon Pilgrim (RKSimon)

Once #160280 has landed all of these functions can be replaced with simple interp__builtin_elementwise_int_unaryop callbacks ``` interp__builtin_parity interp__builtin_clrsb interp__builtin_bitreverse ```

[llvmbot]

Hi!

This issue may be a good introductory issue for people new to working on LLVM. If you would like to work on this issue, your first steps are:

1. Check that no other contributor is working on this issue. If someone is assigned to the issue or claimed to be working on it, ping the person. After one week without a response, the assignee may be changed.
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3. Fix the issue locally.
4. Run the test suite locally. Remember that the subdirectories under test/ create fine-grained testing targets, so you can e.g. use make check-clang-ast to only run Clang's AST tests.
5. Create a Git commit.
6. Run git clang-format HEAD~1 to format your changes.
7. Open a pull request to the upstream repository on GitHub. Detailed instructions can be found in GitHub's documentation. Mention this issue in the description of the pull request.

If you have any further questions about this issue, don't hesitate to ask via a comment in the thread below.

[llvmbot]

@llvm/issue-subscribers-good-first-issue

Author: Simon Pilgrim (RKSimon)

Once #160280 has landed all of these functions can be replaced with simple interp__builtin_elementwise_int_unaryop callbacks ``` interp__builtin_parity interp__builtin_clrsb interp__builtin_bitreverse ```

[donneypr]

Can I please be assigned this task? Thank you!