Plat 9367 thermal state workaround

[kstenerud]

Goal

A bug from iOS 15.0.2 to 15.1.1 causes ThermalStateDidChangeNotification to on rare occasions be posted from within -[NSProcessInfo thermalState], which triggers a recursive call for any listeners since they will in turn call -[NSProcessInfo thermalState] and trigger recursion detection in _os_unfair_lock (_os_unfair_lock_recursive_abort).

See #1511

Ref: https://github.com/Tencent/matrix/blob/master/matrix/matrix-iOS/Matrix/WCCrashBlockMonitor/CrashBlockPlugin/Main/BlockMonitor/WCBlockMonitorMgr.mm#L493

Design

This PR defers the -[NSProcessInfo thermalState] call to a background thread as a workaround.

Testing

Manually tested

[github-actions]

Bugsnag.framework binary size increased by 248 bytes from 706,448 to 706,696

    FILE SIZE        VM SIZE    
 --------------  -------------- 
  +0.1%    +148  +0.1%    +148    __TEXT,__text
  +0.1%    +136  +0.1%    +136    String Table
  +0.1%    +112  +0.1%    +112    Symbol Table
  +1.0%     +32  +1.0%     +32    __DATA,__const
  -0.4%     -32  -0.2%     -32    [__DATA]
  -0.6%    -148  -0.6%    -148    [__TEXT]
  [ = ]       0  -1.7%    -248    [__LINKEDIT]
  +0.0%    +248  [ = ]       0    TOTAL

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[lemnik]

LGTM