Retune nsJSEnvironment

[classilla]

We should probably twiddle with the GC/CC intervals, and there is some Telemetry to remove. While we're at it we should ensure that widget/cocoa/nsIdleServiceX.mm is correctly determining idle time.

[classilla]

Also, javascript.options.mem.gc_high_frequency_time_limit_ms seems a bit high. Perhaps should also be 100ms.

[classilla]

nsIdleServiceX.mm does appear to function correctly.

[classilla]

This is sticking and I don't have any clear reason to keep it open.