DM-32210: Use inspect to determine when we leave the utils module

[timj]

Previously using the filename the code could be confused if
there was another lsst/utils directory in the path. Now
using inspect.getmodule the code can no for sure when it
leaves the lsst.utils module.

Checklist

• ran Jenkins
• added a release note for user-visible changes to doc/changes

[codecov]

Codecov Report

Merging #103 (3d2cd24) into master (25fdfb9) will decrease coverage by 0.07%.
The diff coverage is 75.00%.

@@            Coverage Diff             @@
##           master     #103      +/-   ##
==========================================
- Coverage   90.87%   90.80%   -0.08%     
==========================================
  Files          36       36              
  Lines        2083     2087       +4     
==========================================
+ Hits         1893     1895       +2     
- Misses        190      192       +2     

Impacted Files	Coverage Δ
python/lsst/utils/timer.py	95.00% <75.00%> (-1.88%)	⬇️

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[natelust]

With inspect and frames you need to be very careful about creating local references to frames, as you can create reference cycles, so the fewer local variables you need the better, and cleaning up variables that contain frames before exiting a function is a good idea. This may be overly defensive for how often this function gets used, but it is good practice, especially if someone uses it as a code reference later on.

Suggested change

	if not module.__name__.startswith("lsst.utils"):
	for i, s in enumerate(inspect.stack()):
	module = inspect.getmodule(s.frame)
	if module is None:
	continue
	if not module.__name__.statswith("lsst.utils"):
	stacklevel = i
	break
	del s
	return stacklevel

[timj]

This seems highly unpythonic but I'll make the change.