THRIFT-6071: Validate container size fits int32 range before narrowing conversion in TSimpleJSONProtocol

[Jens-G]

Summary

ParseElemListBegin reads the list/set element count from the wire as int64 via ParseI64, but passes int32(nSize) to checkSizeForProtocol. Values larger than math.MaxInt32 are silently narrowed before the check; the truncated value may pass while the full int64 is stored in size and returned to callers.

The fix adds an explicit range check (nSize > math.MaxInt32) before the narrowing cast, returning SIZE_LIMIT immediately. The existing checkSizeForProtocol call is retained for the normal range.

ReadListBegin and ReadSetBegin both delegate to ParseElemListBegin and are covered by this change. binary_protocol, compact_protocol, and json_protocol read container sizes as int32 directly and are not affected.

Related: PR #3599 addresses an analogous issue in ReadMapBegin; the same guard should be added there once that fix lands.

Test plan

• TestReadSimpleJSONProtocolListBeginSizeOverflow — new test covering list and set; verifies SIZE_LIMIT is returned for a declared size of 1<<32 + 1 (which int32 truncation would reduce to 1)
• Full Go library test suite: go test ./... passes

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