MathTrig - Change Names of funcWhatever to evaluate

[oleibman]

Per discussions while MathTrig was being broken up, this would help standardize the code. That idea was adopted partway through the breakup. This PR applies that standardization to the earlier efforts. A similar effort is required for DateTime; that will come later. This PR replaces #2006.

The only 2 remaining funcWhatevers in MathTrig are both in SUM, which required two different methods depending on whether or not string parameters were to be ignored. It seems appropriate to leave those method names non-standardized in order to require a decision about which is to be used if they are invoked internally.

3 Phpstan grandfathered errors were eliminated as part of this change, and its baseline has changed accordingly.

This is:

- [ ] a bugfix
- [ ] a new feature
- [x] refactoring

Checklist:

• Changes are covered by unit tests
• Code style is respected
• Commit message explains why the change is made (see https://github.com/erlang/otp/wiki/Writing-good-commit-messages)
• CHANGELOG.md contains a short summary of the change
• Documentation is updated as necessary

Why this change is needed?

[oleibman]

@MarkBaker and @PowerKiKi - this change seems a little snakebit. Scrutinizer fails because it received a segfault in phpcs? Even though Github phpcs runs fine? Seems inconceivable that my change has anything to do with the Scrutinizer problem, but, whether or not that's true, I have no idea how to move forward.

[oleibman]

Yay! Changing a comment forced Scrutinizer (and the other tests) to run again, and this time it didn't segfault. So the change is ready.