Add consistency between checkTemplateFileExists functions,

[braders]

Overview

Add consistency between checkTemplateFileExists functions, resolving phpdoc issues in the process.

Before

Each checkTemplateFileExists method in core is fundamentally performing the same job (on different components). Therefore it makes sense for the method comment to match.

In doing so, these methods have a consistent signature, accepting either string|null for $suffix.

The primary benefit of this is that the method in CRM/Profile/Form.php is now correctly documented as accepting a string for $suffix.

After

Consistency added.

[civibot]

(Standard links)

• If this is your first pull-request for CiviCRM, please browse CONTRIBUTING.md for information about the development and testing processes.
• If you are reviewing this pull-request, you may wish to consult the test sites and the Review Standards (long template, short template).

[eileenmcnaughton]

Thanks @braders - another improvement!

[eileenmcnaughton]

This should fix those errors - although I don't know why they popped up #22590

[seamuslee001]

Jenkins re test this please