Echelle improvements

[profxj]

Two changes in this short PR:

1. Allow the usage of use_2dmodel_mask for echelle spectrographs.
2. Turns off re-initializing the reduce_bpm in the final call to global_sky

The 2nd item was leading to crashes in Echelle data when an order had problems
during object finding.

No new tests or docs, but I am going to run the DevSuite.
And the new functionality has been tested on real world X-Shooter data.

[codecov-commenter]

Codecov Report

Merging #1693 (0459298) into develop (b23ec14) will increase coverage by 0.00%.
The diff coverage is 75.00%.

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@@           Coverage Diff            @@
##           develop    #1693   +/-   ##
========================================
  Coverage    41.05%   41.05%           
========================================
  Files          189      189           
  Lines        43568    43570    +2     
========================================
+ Hits         17888    17889    +1     
- Misses       25680    25681    +1     

Files	Coverage Δ
pypeit/core/skysub.py	59.27% <ø> (ø)
pypeit/find_objects.py	46.09% <100.00%> (+0.14%)	⬆️
pypeit/pypeit.py	77.12% <100.00%> (ø)
pypeit/extraction.py	61.93% <0.00%> (-0.22%)	⬇️

[debora-pe]

All looks good. I only have a small comment.
Thanks for doing this @profxj!

[profxj]

tests started

[profxj]

Test Summary

--- PYTEST PYPEIT UNIT TESTS PASSED 239 passed, 70 warnings in 538.67s (0:08:58) ---
--- PYTEST UNIT TESTS PASSED 133 passed, 171 warnings in 990.98s (0:16:30) ---
--- PYTEST VET TESTS PASSED 58 passed, 68 warnings in 1010.66s (0:16:50) ---
--- PYPEIT DEVELOPMENT SUITE PASSED 231/231 TESTS ---
Testing Started at 2023-10-05T16:24:11.656047
Testing Completed at 2023-10-06T07:47:17.898775
Total Time: 15:23:06.242728

[kbwestfall]

Two things: One minor comment on the docstring; and a possible bug I randomly caught that might never get triggered, but makes the code misleading. Approving anyway.