perf: Use bitflags for OptState

[ritchie46]

Brings 14 bytes down to 4.

[codecov]

Codecov Report

Attention: Patch coverage is 95.65217% with 3 lines in your changes missing coverage. Please review.

Project coverage is 80.47%. Comparing base (2eb1ac2) to head (77b6c05).
Report is 2 commits behind head on main.

Files	Patch %	Lines
crates/polars-lazy/src/frame/mod.rs	89.28%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #17788      +/-   ##
==========================================
- Coverage   80.47%   80.47%   -0.01%     
==========================================
  Files        1503     1503              
  Lines      197103   197064      -39     
  Branches     2794     2794              
==========================================
- Hits       158624   158582      -42     
- Misses      37965    37968       +3     
  Partials      514      514              

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