[MAINT] Change clang-format for pre-commit

[ndgrigorian]

This PR proposes

• moving to use mirrors-clang-format for clang-format
• adding .clang-format
• moving to clang-format-22 from clang-format-15

[Copilot]

Pull request overview

This PR updates the repository’s C/C++ formatting tooling by switching the pre-commit clang-format hook to pre-commit/mirrors-clang-format, introducing a project .clang-format configuration, and reformatting existing headers accordingly.

Changes:

• Switch pre-commit clang-format hook source and upgrade to clang-format 22.
• Add a repository-wide .clang-format file and reformat affected headers.
• Record the formatting commit in .git-blame-ignore-revs.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
mkl_fft/src/multi_iter.h	clang-format reflow; touched iterator implementation code.
mkl_fft/src/mklfft.h	clang-format reflow of public C API declarations.
.pre-commit-config.yaml	Switch clang-format hook to mirrors-clang-format and bump version.
.git-blame-ignore-revs	Add ignore entry for the reformatting commit.
.clang-format	New formatting configuration used by clang-format/pre-commit.

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