THRIFT-6055: Limit recursion depth in JavaME struct read/write

[Jens-G]

Summary

THRIFT-6055 — bound the recursion depth of JavaME struct read/write.

On master the generated JavaME read() / write() call readStructBegin /
writeStructBegin directly with no depth bound, TProtocol has no recursion
counter, and TProtocolException has no DEPTH_LIMIT type, so a deeply nested or
cyclic struct is processed without a limit in the generated path.

This PR:

• adds DEPTH_LIMIT = 6 to TProtocolException;
• adds a recursionDepth_ counter with incrementRecursionDepth() /
  decrementRecursionDepth() to TProtocol, bounded at 64;
• updates the JavaME generator to wrap each generated struct read/write body in
  try { … } finally { decrementRecursionDepth(); }. The bound lives only in the
  generated path (one count per struct); readStructBegin / writeStructBegin
  are left untouched, so there is no double-counting.

Unknown-field skipping is handled separately by TProtocolUtil.skip (which
carries its own maxSkipDepth) and is left unchanged here.

Test

The previous test exercised increment/decrementRecursionDepth() in isolation,
which does not cover the real generated read/write path. It is replaced by
lib/javame/test/TestRecursionDepth.java — a generated-code round-trip over the
recursive IDL types in test/Recursive.thrift (CoRec ⇄ CoRec2, RecTree),
run over the binary and JSON protocols:

case	expectation
chain at the limit (64)	round-trips
chain one over (65), write	DEPTH_LIMIT
crafted payload one over (65), read	DEPTH_LIMIT
wide shallow tree (192 siblings)	round-trips (decrement unwinds each sibling)
cyclic graph	DEPTH_LIMIT instead of unbounded recursion

Validation with OpenJDK 17 (against lib/javame/src, excluding the
javax.microedition-only THttpClient):

• with this PR: 12/12 checks pass (6 cases × 2 protocols).
• against unpatched generated code (master behaviour): the 6 over-limit /
  cyclic checks fail — over-limit writes and reads are not rejected and the
  cyclic case recurses to StackOverflowError — confirming the gap this change
  closes.

JavaME has no build harness or CI; the test is a standalone main, and the
generate / compile / run commands are documented in its header.

🤖 Generated with Claude Code

Co-Authored-By: Claude Opus 4.8 noreply@anthropic.com