Avoid a PHP8.4 Deprecation

[oleibman]

Fix #3782. A signature of the ReflectionMethod constructor will be deprecated, and PhpSpreadsheet runs afoul of that change in one place. Php8.4 is not yet available in any form, and I am reluctant to make this change until we see that the issue is real (and that this PR fixes it), so am leaving this PR in draft status till then.

I note that one Excel function PI is implemented not as a class method in PhpSpreadsheet, but rather as a call to the native Php function pi. The ReflectionMethod call is subject to a TypeError in the changed code, but that is already the case. We haven't seen a TypeError because (a) it will arise only if the caller supplies an argument to the function (which must be called with zero arguments), and (b) there are no test cases for that function. The code is slightly cleaned up, and test cases are now added. This is not an important enough problem to rush this PR - the existing code (and the changed code), rather than failing with TypeError, will fail with a CalculationException (wrong number of arguments) before it gets to the TypeError; that is the correct behavior.

This is:

• a bugfix
• a new feature
• refactoring
• additional unit tests

Checklist:

• Changes are covered by unit tests
  • Changes are covered by existing unit tests
  • New unit tests have been added
• 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 and a link to the pull request if applicable
• Documentation is updated as necessary

Why this change is needed?

Provide an explanation of why this change is needed, with links to any Issues (if appropriate).
If this is a bugfix or a new feature, and there are no existing Issues, then please also create an issue that will make it easier to track progress with this PR.