feat(infra): Expose abstract Shard class [CLK-187171]

[Justinon]

Adds abstract Shard class for consumers to extend so name functionality can be standardized and abstracted.
Adds UTs for Shard abstract class.

[codecov]

Codecov Report

Merging #3 (2bfcb38) into main (b0c3262) will increase coverage by 20.33%.
The diff coverage is 100.00%.

Additional details and impacted files

@@             Coverage Diff              @@
##             main        #3       +/-   ##
============================================
+ Coverage   79.66%   100.00%   +20.33%     
============================================
  Files           3         3               
  Lines         118       137       +19     
  Branches        4         2        -2     
============================================
+ Hits           94       137       +43     
+ Misses         24         0       -24     

Impacted Files	Coverage Δ
src/Shard.ts	100.00% <100.00%> (+100.00%)	⬆️
src/index.ts	100.00% <0.00%> (+100.00%)	⬆️

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