Add support for PEXPIREAT's options

[dogukanteber]

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Description of change

closes #1939

[chayim]

@dogukanteber WDYT about making these options (NX, XX, etc) variables in the function header. IMHO it would watch our other functions.

[codecov-commenter]

Codecov Report

Merging #2027 (8d8e2e8) into master (8d949a3) will decrease coverage by 0.11%.
The diff coverage is 35.71%.

@@            Coverage Diff             @@
##           master    #2027      +/-   ##
==========================================
- Coverage   92.17%   92.05%   -0.12%     
==========================================
  Files         100      100              
  Lines       21024    21064      +40     
==========================================
+ Hits        19378    19391      +13     
- Misses       1646     1673      +27     

Impacted Files	Coverage Δ
tests/test_commands.py	98.22% <25.80%> (-0.78%)	⬇️
redis/commands/core.py	85.70% <63.63%> (-0.17%)	⬇️
redis/asyncio/client.py	90.45% <0.00%> (-0.18%)	⬇️
tests/test_cluster.py	98.29% <0.00%> (ø)
redis/asyncio/connection.py	82.77% <0.00%> (+0.11%)	⬆️

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[dvora-h]

@dogukanteber I pushed a small fix so the options will be consistent with options in other functions (like set etc.), now it's ready and we'll include it in the next release, thank you!