feat(client): V2 API client ratelimit improvements

[jharley]

This change teaches the V2 API client to respond to HTTP429s by backing off using the Ratelimit headers in the API's response.

• Closes V2 API Client gracefully handles rate limits observing Rate-Limit headers #511

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 67.24138% with 19 lines in your changes missing coverage. Please review.

Project coverage is 78.57%. Comparing base (1c9409a) to head (ac2b603).

Files	Patch %	Lines
client/v2/client.go	21.42%	8 Missing and 3 partials ⚠️
client/v2/limits.go	85.71%	4 Missing and 2 partials ⚠️
client/client.go	0.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #519      +/-   ##
==========================================
- Coverage   78.63%   78.57%   -0.07%     
==========================================
  Files          72       73       +1     
  Lines        5557     5606      +49     
==========================================
+ Hits         4370     4405      +35     
- Misses        901      910       +9     
- Partials      286      291       +5     

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