fix: psubscribe method issues

[tanmaykm]

• reduce specialization of psubscribe and subscribe method signatures
• fix typo in call to _psubscribe
• introduced psubscribe_data similar to what was done in fix subscription callback invoke and pubsub tests #95
• improve tests for psubscribe and subscribe

depends on #100
fixes #101

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (b76a05f) 73.88% compared to head (91ded87) 80.21%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #102      +/-   ##
==========================================
+ Coverage   73.88%   80.21%   +6.32%     
==========================================
  Files           6        6              
  Lines         360      369       +9     
==========================================
+ Hits          266      296      +30     
+ Misses         94       73      -21     

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[jkaye2012]

Give #100 is merged, should we look at this one as well?

[tanmaykm]

Thanks @jkaye2012 !
I have rebased and this is ready for review.