Check an annotated anonymous class creation against the declaration bound on all JDKs

[aosen-xiong]

Fixes #2009.

new @A AClass() {} is validated against AClass's declaration bound on Java 17 and later but not
on Java 11, so the same source checks differently depending on the compiler. #1909 unified how
anonymous classes are recognized, but this path was left behind.

Two things block it on Java 11, and neither alone changes the result:

TreeUtils.isTypeTree answered from the tree kind alone, which the TODO it carried admitted is an
under-approximation. BaseTypeValidator uses it to decide whether to validate a type that is
syntactically an expression, and on Java 11 the extends clause of an annotated anonymous class is a
bare identifier, so validation was skipped. It now resolves what the identifier, or member select,
refers to. The member-select case has no test: an annotated qualified type is Outer.@Anno Inner,
which arrives as an ANNOTATED_TYPE and was already handled, so only the unannotated form reaches
that branch and it has no annotation to validate.

The clause also carries no annotation on Java 11: javac attaches it to the anonymous class body's
modifiers rather than to the clause, a difference getExplicitNewClassAnnos already reconciles.
getTypeOfExtendsImplements applies those annotations to the clause's type, after
addComputedTypeAnnotations, whose defaulting would otherwise overwrite them.

Note for reviewers: isTypeTree is public API

TreeUtils.isTypeTree is public and its contract changes here. It was a pure kind test, answerable
for any tree; it now resolves an identifier or member select through elementFromTree, so it
requires an attributed tree. A caller that passes an unattributed tree gets a different answer than
before.

Inside this repository there are exactly two callers, and only one is affected:

• GenericAnnotatedTypeFactory.getAnnotatedTypeLhs calls it in the default: branch of a switch
  on the tree kind. IDENTIFIER and MEMBER_SELECT are handled by earlier cases in that switch and
  never reach default:, so the new behaviour cannot be observed there.
• BaseTypeValidator.shouldCheckTopLevelDeclaredOrPrimitiveType is the intended target, and is
  where the anonymous-class fix takes effect.

🤖 Generated with Claude Code

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[wmdietl]

Thanks! Please look at my refactorings.

[aosen-xiong]

Thanks! This looks good.