[core] XPath cleanups

[adangel]

Describe the PR

• Small changes:
  • package move of XPathRule to n.s.pmd.lang.rule.xpath
  • remove the deprecation version property - that means, setting a property version in ruleset.xml now creates an error
• Bigger changes:
  • For implementing custom XPath function, we now have an own API in PMD (See classes/interfaces n.s.pmd.lang.rule.xpath.impl.XPathFunctionDefinition). This avoids the direct dependency on Saxon - Saxon is only used for the implementation (in internal packages).
  • The API only supports what we currently use and doesn't expose every feature from Saxon. So, in case something is missing for a future custom XPath function, we need to extend the API.
  • There is currently no documentation (as far as I know) that explains how to implement a custom XPath function. See [doc] How to implement a custom XPath function for a language #4807.
  • This API is anyway new with PMD 7, so no need to updating migration guide etc. Right now, the API lives in impl, so it is for now anyway considered internal.

Related issues

• Fixes [core] Cleanups in XPath area #4309

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 0 violations, introduces 0 new violations, 0 new errors and 0 new configuration errors, removes 0 violations, 0 errors and 0 configuration errors. Download full report as build artifact
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✅	Compared to master: This changeset changes 0 violations, introduces 0 new violations, 0 new errors and 0 new configuration errors, removes 0 violations, 0 errors and 0 configuration errors. Download full report as build artifact

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