Add Command Line Arguments to DefaultContext

[jayhf]

The command line arguments seem like a really useful piece of information to have when debugging crashes. This adds them to the DefaultContext so that they're readily available in Sentry

[tustanivsky]

Hey @jayhf, I believe we're already adding the command line input to Crash Info context on Win/Linux for captured crash events:

sentry-unreal/plugin-dev/Source/Sentry/Private/Desktop/CrashReporter/SentryCrashContext.cpp

Line 54 in 982894b

ContextValues.Add("Command Line", FString(SessionContext.CommandLine).TrimStart());

Does it miss some bits of info you expect to be there along with other CL arguments?