xml: extend RemoveEmptyXmlTags with XPath whitelist, file matcher, and file deletion

[Jenson3210]

Summary

• Extends org.openrewrite.xml.RemoveEmptyXmlTags with three optional, JSON-deserializable options so it can serve as the generic cleanup recipe described in moderneinc/customer-requests#2460 §11:

• xPaths — whitelist of XPath expressions identifying which empty tags are eligible for removal. Attribute predicates are reinterpreted as an attribute allowlist: a candidate tag matches only when its attribute set is a subset of the union of attribute names appearing in the matched predicates. @* is the wildcard, @name enumerates a single allowed name, and @a or @b allows either. So /server only matches attribute-free <server> tags, while /server[@*] matches any, /server[@description] matches no-attribute or description-only servers, and /server[@description or @other] matches when attributes are a subset of {description, other}.

• fileMatcher — glob restricting which files the recipe touches (wired via Preconditions.check(new FindSourceFiles(...), …)).

• deleteFileIfEmpty — when the root tag itself would be a removal candidate, delete the entire source file. Defaults to true.

The visitor is wrapped in Repeat.repeatUntilStable(..., 50) so nested empties cascade and trigger file deletion in a single recipe run. The original no-arg constructor is preserved via Lombok @NoArgsConstructor(force = true), and the explicit all-args constructor is @JsonCreator-annotated. Existing callers and tests are unaffected — the defaults reproduce the prior behavior on documents whose root retains content.

Motivating example (Liberty mp-telemetry.xml cleanup once another recipe strips <feature>mpTelemetry-2.0</feature>):

new RemoveEmptyXmlTags(
    List.of("/server/featureManager", "/server[@*]"),
    "**/mp-telemetry.xml",
    true)

collapses the now-empty <featureManager>, then <server> (the [@*] opts in to its description attribute), then deletes the file.

Test plan

• ./gradlew :rewrite-xml:test --tests "org.openrewrite.xml.RemoveEmptyXmlTagsTest" — 14 tests pass (3 original + 11 new covering file deletion, attribute-allowlist semantics, fileMatcher scoping, and multi-level nested collapse).
• ./gradlew :rewrite-xml:recipeCsvGenerate regenerates rewrite-xml/.../recipes.csv; recipeCsvValidateContent passes.
• ./gradlew :rewrite-xml:licenseMain :rewrite-xml:licenseTest pass.