[clang-tools-extra] [clang-tidy] Make readability-redundant-inline-specifier diagnose `static inline` outside header files (PR #223501)

[via cfe-commits]

================
@@ -270,6 +270,12 @@ infrastructure are described first, followed by tool-specific sections.
   exclusively for overload resolution. Added the {option}`IgnoredTypes`
   option to allow customizing the set of ignored types.
 
+- Improved {doc}`readability-redundant-inline-specifier
+  <clang-tidy/checks/readability/redundant-inline-specifier>` check by flagging
+  `static inline` declarations outside of header files and suggesting `static`
+  alone. This is enabled by default and can be turned off with the new
+  {option}`DiagnoseStaticInline` option.
----------------
EugeneZelenko wrote:

```suggestion
  {option}`DiagnoseStaticInline`.
```

https://github.com/llvm/llvm-project/pull/223501