fix: panics when creating delta tables in threads

[PeterKeDer]

Description

Loading in delta tables from multiple threads is causing panics. Reproducible example:

from multiprocessing.pool import ThreadPool
from deltalake import DeltaTable

def make_dt(x):
    return DeltaTable('/path/to/some/local/table')

pool = ThreadPool(processes=16)
list(pool.map(make_dt, range(16)))

causes

pyo3_runtime.PanicException: Failed to record PID for tokio runtime.: 71866

This race condition is caused by multiple threads trying to acquire and set the PID. Multiple threads could succeed at the PID.get() call at time before any threads set the PID, but only one thread can successfully call PID.set, causing the remaining threads to panic.

This fixes by using get_or_init for setting PID, and only panics if the returned runtime_pid is different from the current pid.

Related Issue(s)

• closes Panic in python > 0.18.2 and <= 0.20.0 around tokio runtime #2905

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 10 lines in your changes missing coverage. Please review.

Project coverage is 72.45%. Comparing base (ef4e4a3) to head (c813ab7).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
python/src/utils.rs	0.00%	10 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2940      +/-   ##
==========================================
+ Coverage   72.43%   72.45%   +0.01%     
==========================================
  Files         131      131              
  Lines       40545    40542       -3     
  Branches    40545    40542       -3     
==========================================
+ Hits        29369    29373       +4     
+ Misses       9293     9292       -1     
+ Partials     1883     1877       -6     

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