Make pytsk/libtsk thread safe

[joachimmetz]

Currently pytsk/libtsk is not thread safe. Recent changes introduced threading compatibility. Note that thread safety has not been sufficiently tested.

Use at your own risk.

Reminder from the README:

WARNING: use pytsk at your own risk. libtsk is known to have many defects. For
processing data from untrusted sources it is highly recommended to add
additional security measures, such as a security sandbox.

@greateggsgreg FYI

[greateggsgreg]

Thanks @joachimmetz . The PR I have open has tests that (I think) extensively test the thread safety. I've been using these changes under for a heavily parallel workload, which has yielded more issues that get fixed in the branch. Hopefully we can get to a better state, but all good with the warning

[greateggsgreg]

PR Split

This monolithic change set has now been split into a few PRs.

• PR 1: Added free-threaded Python 3.14 (3.14t) test #129 - Infrastructure-only change that adds Python 3.14 free-threaded (3.14t) to the CI matrix so subsequent free-threading work can actually be tested on CI.
• PR 2: Improved sanity checks in tsk3.cpp and class_parser.py with regression tests #130 - Defensive sanity checks across the C extension and the wrapper code generator
• PR 3: free-threading PR 3 - Cyclic GC support for generated wrappers (stacked on #130) #131 - Cyclic GC support for wrappers
• PR 4: free-threading PR 4 - Per-instance locking and thread-safety tests #133 - Thread safety fixes and locks
• PR 5: free-threading PR 5 - Thread-safety / free-threaded fixes with tests #120 - Remaining free-threaded specific compatibility fixes