Enable and apply clang-tidy readability and misc fixes.

[Skylion007]

Description

• Broke off this PR from the beefer performance once. This just applies some automated fixes to the code base. The main one is a redundant function ptr dereference and forgetting to mark a bunch const methods as such. Enables a bunch of other checks that ensure modern code.

There is one readability improvement with const return types I would like to enable but it causes error sadly that need to be fixed.

Suggested changelog entry:

* Enable and apply checks for more misc, readability, and code modernization improvements to the codebase. Remove redundant function ptr dereference, makes methods const, and uses member-initializers when possible to allow for trivial construction.

[Skylion007]

This check discourages the user of throw, but since these are explicilty deprecated tests, I add nolints to prevent them from being changed.

[Skylion007]

Ping @rwgk@henryiii

[rwgk]

Thanks Aaron!

[henryiii]

This all looks very good to me! Thanks! Love seeing that someone is finally filling out the clang-tidy checks, see my comment at #2478 (comment) :)

[henryiii]

I'm calling this a fix due to the fact that adding const technically is better, as you can only call const methods on a const object.