Perform session gating asynchronously

[fractalwrench]

Goal

Performs session gating asynchronously. #55 pointed out that this is something we can feasibly do when saving sessions.

Testing

Updated unit test coverage.

[codecov]

Codecov Report

Merging #67 (967e318) into master (ef6fc3b) will increase coverage by 0.00%.
Report is 1 commits behind head on master.
The diff coverage is 84.84%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #67   +/-   ##
=======================================
  Coverage   76.03%   76.03%           
=======================================
  Files         309      309           
  Lines       10046    10041    -5     
  Branches     1447     1447           
=======================================
- Hits         7638     7635    -3     
+ Misses       1820     1818    -2     
  Partials      588      588           

Files	Coverage Δ
...ace/android/embracesdk/injection/DeliveryModule.kt	100.00% <100.00%> (ø)
...race/android/embracesdk/injection/SessionModule.kt	100.00% <ø> (ø)
...brace/android/embracesdk/session/SessionHandler.kt	88.84% <100.00%> (-0.43%)	⬇️
...mbracesdk/comms/delivery/EmbraceDeliveryService.kt	61.60% <82.75%> (+0.76%)	⬆️

... and 1 file with indirect coverage changes

[bidetofevil]

Nice