feat(injected-method): Replace IMailer::validateMailAddress

[nickvergessen]

Motivation and context

• 1 Commit: I made the recently added Rector more generic, so we don't need a new class for each deprecation.
• 2 Commit: Sample of replacing IMailer::validateMailAddress with IEmailValidator::isValid including full test set for a new Nextcloud version: 115 lines 🤩
  Ref fix(mailer): Fix IMailer deprecation message nextcloud/server#59955

How has this been tested?

• Fully covered by unit tests on Set level

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

PR checklist

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING.md document.
• I have added tests to cover my changes.