Note to mergers: Do not merge this commit to 10.5+. An additional PR
will be created for the 10.5 branch which is compatible with later
branches.

Include cppcheck and FlawFinder for SAST scanning.

From 10.6, cherry-picked 12bf5c46 (Remove unused French translations in
Connect engine) and c6072ed9 (Ensure that source files contain only
valid UTF8 encodings). Necessary for FlawFinder to execute and useful
anyway.

Removing MSAN build and test as it was not introduced until 10.5 and
does not successfully build.

Remove failing upgrade test since Fedora installs MariaDB 10.5 and the
10.5->10.4 upgrade rightfully complains

Add to skiplist failing test: main.func_math (MDEV-20966)

All new code of the whole pull request, including one or several files
that are either new files or modified ones, are contributed under the
BSD-new license. I am contributing on behalf of my employer
Amazon Web Services, Inc.