Topic: search_generator refactor

[SpicyGarlicAlbacoreRoll]

• Fixes search_generator() wrongly marking results as incomplete
• Removes some repeat lines of code in search_generator
• use tenacity for verifying and retrying CMR responses (sometimes returned page sizes are not 250)

[codecov-commenter]

Codecov Report

Merging #216 (b6941cb) into master (330efdd) will decrease coverage by 0.13%. The diff coverage is 97.56%.

:exclamation: Current head b6941cb differs from pull request most recent head f1781f5. Consider uploading reports for the commit f1781f5 to get more accurate results

@@            Coverage Diff             @@
##           master     #216      +/-   ##
==========================================
- Coverage   89.86%   89.73%   -0.13%     
==========================================
  Files          52       52              
  Lines        1964     1959       -5     
==========================================
- Hits         1765     1758       -7     
- Misses        199      201       +2     

Flag	Coverage Δ
unittests	89.73% <97.56%> (-0.13%)	:arrow_down:

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Files Changed	Coverage Δ
asf_search/search/search_generator.py	94.78% <97.29%> (-1.12%)	:arrow_down:
asf_search/exceptions.py	100.00% <100.00%> (ø)
asf_search/search/baseline_search.py	94.23% <100.00%> (-1.85%)	:arrow_down:
asf_search/search/search_count.py	100.00% <100.00%> (ø)