Expand Firefox PerfStats collection to new metrics, 64bit

[acreskeyMoz]

We will have to wait until a bug in Firefox is fixed before adding this (otherwise debug builds will assert) https://bugzilla.mozilla.org/show_bug.cgi?id=1977673

But I wanted to create the pull request anyway

[mstange]

Fixes #2313.

[soulgalore]

Cool, feel free to merge it when you feel that everything is ready.