`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