fix(oom): Improve background app state detection

[kattrali]

Goal

Correctly determine foreground/active state when the app is launched via a background fetch or media playback event or extension, or is interrupted by Siri or a phone call. These cases should be regarded as in the background or inactive respectively.

Changeset

• Added detection for app extension state
• Added initial app state (foreground and active) checking

Tests

• Added additional end-to-end tests for when the app is interrupted and will terminate normally (for completeness)

[codecov]

Codecov Report

Merging #394 into master will decrease coverage by 0.23%.
The diff coverage is 46.42%.

@@            Coverage Diff             @@
##           master     #394      +/-   ##
==========================================
- Coverage    52.6%   52.36%   -0.24%     
==========================================
  Files          65       65              
  Lines        7454     7497      +43     
==========================================
+ Hits         3921     3926       +5     
- Misses       3533     3571      +38

Impacted Files	Coverage Δ
...SCrash/Source/KSCrash/Recording/BSG_KSSystemInfo.h	100% <ø> (ø)	⬆️
Source/BugsnagBreadcrumb.m	83.24% <0%> (ø)	⬆️
...SCrash/Source/KSCrash/Recording/BSG_KSSystemInfo.m	75.19% <100%> (+1.53%)	⬆️
Source/BugsnagNotifier.m	51.89% <37.03%> (-0.16%)	⬇️
Source/BSGOutOfMemoryWatchdog.m	28.47% <9.09%> (-1.9%)	⬇️
Source/BugsnagLogger.h	66.66% <0%> (-33.34%)	⬇️
Source/BugsnagSessionTrackingApiClient.m	78.72% <0%> (-8.52%)	⬇️
Source/BugsnagFileStore.m	62.85% <0%> (-6.67%)	⬇️

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[fractalwrench]

Left a few comments inline that'd be good to address/resolve, particularly the breaking change/mazerunner comments. Overall this seems like a good approach, although it'd be good to have a bit more background on how this could be tested for the purposes of code review.