refactor: switch to lower-case float literal suffix (f)

[bkueng]

The original intent behind the check was only for L, as l is similar to 1. https://clang.llvm.org/extra/clang-tidy/checks/readability/uppercase-literal-suffix.html

And some other clang-tidy changes:

• ignore very verbose misc-include-cleaner
• message_compatibility_check: move static methods to anonymous namespace