feat(performance): start transaction for fasthttp integration

[aldy505]

I realized that only a few integration starts performance span for their HTTP handlers (such as net/http and Gin), the others are not. Here is my effort on fixing it for other integrations/frameworks.

This also introduces the GetTransactionFromContext function that takes the fasthttp.RequestCtx as input and returns *sentry.Span or nil. It handles that fasthttp.RequestCtx's context is not compatible with our sentry.GetHubFromContext due to different format of context key.

Discord link: https://discord.com/channels/621778831602221064/621786587939864586/1157114103156969513

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.93%. Comparing base (5942155) to head (0623e4a).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #723      +/-   ##
==========================================
+ Coverage   81.84%   81.93%   +0.08%     
==========================================
  Files          48       48              
  Lines        4759     4782      +23     
==========================================
+ Hits         3895     3918      +23     
  Misses        725      725              
  Partials      139      139              

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