[core] Rules with the same regex properties should be equal

[adangel]

Describe the PR

Found this while upgrading PMD Eclipse Plugin to 7.0.0. In the plugin, we often verify that we have the same ruleset active by executing RuleSet#equals(). This doesn't work as soon as a rule uses java.util.regex.Pattern based properties. The reason is, that Pattern doesn't override equals - see also https://stackoverflow.com/questions/52103427/why-these-two-java-util-pattern-are-not-equal

Ready?

• Added unit tests for fixed bug/feature
• Passing all unit tests
• Complete build ./mvnw clean verify passes (checked automatically by github actions)
• Added (in-code) documentation (if needed)

[pmd-test]

	1 Message
📖	Compared to master: This changeset changes 5 violations, introduces 1 new violations, 0 new errors and 0 new configuration errors, removes 1 violations, 0 errors and 0 configuration errors. Full report
✅	Compared to master: This changeset changes 6 violations, introduces 1 new violations, 0 new errors and 0 new configuration errors, removes 1 violations, 0 errors and 0 configuration errors. Full report

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