(clang-tidy): Enable static downcast and decl naming check

[Skylion007]

Description

• Enable a clang-tidy check to ensure we don't do static_cast for downcasting and always use dynamic_cast. This is safer, more likely to be correct, and most compilers will optimize them to be the same speed anyway if valid. There are no other changes to the codebase currently since we do it properly, but this check ensures the regression doesn't get introduced in a PR.
• Also enables another check that looks for inconsistent naming between forward declarations and their implementations. This is unlikely to occur in the code base, but ensures no regressions get introduced.

Suggested changelog entry:

* Enable cppcoreguidelines-pro-type-static-cast-downcast and readability-inconsistent-declaration-parameter-name in clang-tidy.

[rwgk]

Nice!