Run the `clang-format.bash` script to update all our C and C++ code to a
new style defined by `.clang-format`, now with "east const" enforcement.
Use `clang-format` version 18.
* If you reached this commit for a line in `git blame`, re-run the blame
operation starting at the parent of this commit to see older history
for the content.
* See the parent commit for instructions to rebase a change across this
style transition commit.
Issue: #26123
`cmake_path(GET "foo/.." STEM out)` is supposed to set `out` to `".."`,
the entire `cmake_path(GET "foo/.." FILENAME)` result.
However, the `GetNarrowStem()` logic in `cmCMakePath` was lacking
the `.` and `..` special-casing logic present in other methods.
As a result, it would erroneously trim the second `.` off of a stem
of `..` and return only `.`.
This caused the result of `cmake_path(GET "foo/.." STEM)` to be `"."`.
Making the standard empty-or-.-or-.. checks and bailing out early
fixes the result of `cmCMakePaths{".."}.GetNarrowStem()`.
Fixes: #26235
