Add in_foreground app context for crashes

[philipphofmann]

Description

The app context in_foreground doesn't work for crashes. SentryCrash already stores this information in the crash report:

sentry-cocoa/Sources/SentryCrash/Recording/SentryCrashReport.c

Lines 1350 to 1351 in 07ea386

	writer->addBooleanElement(
	writer, SentryCrashField_AppInFG, monitorContext->AppState.applicationIsInForeground);

The SentryCrashReportConverter only needs to add the in_foreground app context by reading the state from the SentryCrashField_AppInFG from the crash report.

Related to #4559.