Add missing functions to python

[jgoday]

Which issue does this PR close?

Closes #374.

Rationale for this change

Complete python functions from logical_plan.

What changes are included in this PR?

Export python functions from logical_plan:

• array
• ascii
• sum
• bit_length
• btrim
• character_length
• chr
• concat_ws
• in_list
• initcap
• left
• lower
• lpad
• ltrim
• md5
• octet_length
• regexp_replace
• repeat
• replace
• reverse
• right
• rpad
• rtrim
• sha224
• sha256
• sha384
• sha512
• split_part
• starts_with
• strpos
• substr
• to_hex
• translate
• trim
• upper

Are there any user-facing changes?

Update or add python binding docs.

[jimexist]

related #389

[jorgecarleitao]

Thanks a lot, @jgoday ! Looks great.

I do not think we need to test these: we have demonstrated that the logic works for the others, and these are essentially using the same implementation, both in DataFusion and in the wrapper.

[codecov-commenter]

Codecov Report

Merging #388 (5d0a725) into master (db4f098) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #388   +/-   ##
=======================================
  Coverage   74.94%   74.94%           
=======================================
  Files         146      146           
  Lines       24314    24314           
=======================================
  Hits        18221    18221           
  Misses       6093     6093           

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[Dandandan]

LGTM! 💯