Use a threadsafe map to make getActiveSpans threadsafe

[bidetofevil]

Goal

The underlying snapshot taking operation isn't thread safe, so we have to use a thread safe data structure to ensure we can snapshot the current active spans while is being modified. This leaves room for some race conditions as to which session a span is started or stopped in, which is probably fine given the asynchronous nature of tracking spans anyway.

What I don't want is to lock everything every time a span is started or stopped, which could potentially result in some pretty bad performance. I can take a look to see if we can have some greater guarantees to reduce the aforementioned race condition, but this will work fine for now as long as we don't mind a bit of timestamp misalignment between span and session boundaries.

[bidetofevil]

• Use a threadsafe map to make getActiveSpans threadsafe #888 👈
• master

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.91%. Comparing base (6e92cf7) to head (70ab85f).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #888   +/-   ##
=======================================
  Coverage   80.91%   80.91%           
=======================================
  Files         435      435           
  Lines       11613    11613           
  Branches     1764     1764           
=======================================
  Hits         9397     9397           
  Misses       1438     1438           
  Partials      778      778           

Files	Coverage Δ
...ndroid/embracesdk/internal/spans/SpanRepository.kt	86.95% <100.00%> (ø)

... and 2 files with indirect coverage changes

[priettt]

LGTM!