Removed unused funcs from _libs

[jbrockmendel]

See coverage report: #18512 (comment)

This just removes a handful of unused functions. LMK if some should be kept around just-in-case.

Not included in the never-used group but worth mentioning: lib.fast_unique, lib.convert_timestamps, and lib.string_array_replace_from_nan_rep are each called exactly once in io.pytables, not covered in tests (io.pytables looks poorly covered, might have had a bunch of skipTests locally)

• closes #xxxx
• tests added / passed
• passes git diff upstream/master -u -- "*.py" | flake8 --diff
• whatsnew entry

[codecov]

Codecov Report

Merging #18533 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #18533      +/-   ##
==========================================
- Coverage   91.35%   91.33%   -0.02%     
==========================================
  Files         164      164              
  Lines       49801    49801              
==========================================
- Hits        45494    45485       -9     
- Misses       4307     4316       +9

Flag	Coverage Δ
#multiple	89.13% <ø> (ø)	⬆️
#single	40.81% <ø> (-0.07%)	⬇️

Impacted Files	Coverage Δ
pandas/io/gbq.py	25% <0%> (-58.34%)	⬇️
pandas/core/frame.py	97.81% <0%> (-0.1%)	⬇️

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[jreback]

do u have linting settings that show these?
if so they should be put up as well

[jbrockmendel]

do u have linting settings that show these?

You mean show that they are unused? I didn't know linting could do that. No, this is just based on grepping and seeing only the definition.

[jreback]

yes might be a way to do this more automatically

[jbrockmendel]

If you find such a way let me know. Until then, any objection to PRing them manually as I find them?

[jreback]

yeah sometimes things build up. thanks!

[jreback]

Not included in the never-used group but worth mentioning: lib.fast_unique, lib.convert_timestamps, and lib.string_array_replace_from_nan_rep are each called exactly once in io.pytables, not covered in t

yeah these were put in here for lack of a better location. we could add a separate small lib for this to reduce lib.pyx size if it helps.