Optimize payload queue for write path

[sukunrt]

Follow up to #319
This optimizes the payload Queue for the write path by doing sorted inserts to the tsns slice.

[codecov]

Codecov Report

Attention: Patch coverage is 78.94737% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 80.76%. Comparing base (c04adbf) to head (278dfbb).

Files	Patch %	Lines
payload_queue.go	77.77%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@                Coverage Diff                @@
##           chunk-tracker     #320      +/-   ##
=================================================
+ Coverage          80.63%   80.76%   +0.13%     
=================================================
  Files                 50       50              
  Lines               4280     4211      -69     
=================================================
- Hits                3451     3401      -50     
+ Misses               682      663      -19     
  Partials             147      147              

Flag	Coverage Δ
go	80.76% <78.94%> (+0.13%)	⬆️
wasm	67.22% <78.94%> (-0.09%)	⬇️

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