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
`include-what-you-use` diagnostics, in practice, are specific to
the environment's compiler and standard library. Update includes
to satisfy IWYU for our CI job under Debian 12.
Add `--test-output-truncation` to `ctest`. This option can be used to
customize which part of the test output is being truncated. Currently
supported values are `tail`, `middle` and `head`.
Also add equivalent `CTEST_CUSTOM_TEST_OUTPUT_TRUNCATION` variable.
Fixes: #23206
