Support JDK 27 end positions (JDK-8372948)

[slachiewicz]

Before this PR

JDK-8372948 (JDK 27) removed EndPosTable and JCCompilationUnit.endPositions, so Trees.getEndPosition, StringWrapper and RemoveUnusedImports fail with NoSuchFieldError on JDK 27. The same change re-ordered the four-argument ParserFactory.newParser, so Formatter was passing parseModuleInfo=true on JDK 27 without noticing. Fixes #1785.

After this PR

==COMMIT_MSG==
Support JDK 27 end positions (JDK-8372948)

Trees now looks up the end-position API once through a method handle: JCTree.getEndPosition() on JDKs without EndPosTable, and getEndPosition(unit.endPositions) via a VarHandle on older ones. All three call sites go through it, and Trees.newParser passes the parser flags in the order each JDK generation expects. Same approach as google/google-java-format#1328.
==COMMIT_MSG==

Verified: ./gradlew :palantir-java-format:check → 1405 tests pass; the built CLI formats identically on JDK 26 and JDK 27.

Possible downsides?

The handle is resolved from class presence, not from the runtime version number, so an early-access build that has one half of JDK-8372948 but not the other would fail at class init instead of at the first formatted file. No such build exists in the released tags.

This change was created with AI assistance.

[palantirtech]

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Description

Support JDK 27 end positions (JDK-8372948)

Trees now looks up the end-position API once through a method handle: JCTree.getEndPosition() on JDKs without EndPosTable, and getEndPosition(unit.endPositions) via a VarHandle on older ones. All three call sites go through it, and Trees.newParser passes the parser flags in the order each JDK generation expects. Same approach as google/google-java-format#1328.

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