[pdata] Deprecate Flags and SetFlags

[TylerHelmuth]

Description:
Deprecates Flags and SetFlags in favor of FlagsStruct

Link to tracking Issue:
#5443

Testing:
Unit tests

[codecov]

Codecov Report

Merging #5790 (b0416e4) into main (eb47b38) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #5790      +/-   ##
==========================================
+ Coverage   91.49%   91.50%   +0.01%     
==========================================
  Files         192      192              
  Lines       11437    11433       -4     
==========================================
- Hits        10464    10462       -2     
+ Misses        778      777       -1     
+ Partials      195      194       -1     

Impacted Files	Coverage Δ
pdata/internal/generated_pmetric.go	97.33% <ø> (-0.05%)	⬇️
pdata/internal/metrics.go	82.63% <100.00%> (+1.84%)	⬆️
processor/batchprocessor/batch_processor.go	89.63% <0.00%> (-1.04%)	⬇️
pdata/internal/common.go	95.38% <0.00%> (+0.76%)	⬆️

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