[3.13] gh-128679: Fix tracemalloc.stop() race conditions (#128897)

tracemalloc_alloc(), tracemalloc_realloc(), PyTraceMalloc_Track(),
PyTraceMalloc_Untrack() and _PyTraceMalloc_TraceRef() now check
tracemalloc_config.tracing after calling TABLES_LOCK().

_PyTraceMalloc_Stop() now protects more code with TABLES_LOCK(),
especially setting tracemalloc_config.tracing to 1.

Add a test using PyTraceMalloc_Track() to test tracemalloc.stop()
race condition.

Call _PyTraceMalloc_Init() at Python startup.