[clang] [clang-format] Extract utility functions outside of test fixture (PR #78108)

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seranu wrote:

> Am I missing someone but how do you plan on using these functions if they are in an anonymous namespace in the file and not part of a class where they are static? maybe I missed something.

I am planning to define other test fixtures in the same file. I need to do it as I want to add parametrized tests for DefinitionBlockSeparator and need a new test fixture for that. The proposal is available for reference here: https://github.com/llvm/llvm-project/pull/77918/files#diff-a3ebb77dfe5a0623927f138f1689854ca47ff0f3bba6386850090e781935c4c7



https://github.com/llvm/llvm-project/pull/78108