Check IdentityHashMap method arguments for value classes

[jihxonx]

Summary

ValueClassIdentity checks the type arguments at the construction site, so a map
declared with Object type arguments hides the problem:

IdentityHashMap<Object, Object> map = new IdentityHashMap<>();
map.put(LocalDate.of(2026, 8, 14), "x");
map.put(LocalDate.of(2026, 8, 14), "y");
System.out.println(map.size());

On Temurin 28-ea+11 with --enable-preview this prints 1 instead of 2, and
javac -Xlint:all reports nothing. The same applies where the map is a parameter
or field, since the construction site may not be in the same compilation unit.

• Report value-based expressions passed directly to identity-sensitive IdentityHashMap methods.
• Handle containsKey, containsValue, get, put, putIfAbsent, and remove.
• Match IdentityHashMap subclasses while avoiding unrelated overloads.
• Keep the analysis local to the invocation and avoid dataflow or interprocedural tracking.
• Check both key and value positions that use reference identity, including the value argument of remove(Object, Object).

Test

• mvn -pl core test "-Dtest=ValueClassIdentityTest"

Follow-up to #6029