Now clang-format report will skip files matching `clang-format.ignore`.
For now it's empty.
clang-tidy will not receive diffs for `clang-tidy.ignore` (it still can
produce warnings for these files).
In addition build bot will not will not post comments for files
that are matched by `clang-tidy-comments.ignore`. Now project/file should
be whitelisted to receive inline comments from clang-tidy.
Added all /test directories to `clang-tidy.ignore`.
Other alternatives considered:
- using 'compile_commands.json': does not contain header files.
- specifying -regex option to 'clang-tidy-diff': probably not the best
experience of providing multiple rules and maintaining a single regex.
