port legacyfox to ecmascript modules

port legacyfox to ecmascript modules

mozilla calls this 'esm-ification'. the last relevant to us modules were
ported in mozilla124[1], so this is our new minimum version. the old
version will likely be compatible with firefox up to version 128esr[2].

static imports are not supported in autoconfig scripts. i tried to keep
the diff as small as possible w.r.t comm-central's final JSMs. because
of this, we don't lazy-load any modules any more, nor provide any lazy
getters, as they would need to be loaded into a `lazy` object instead
the global (`this`) namespace, causing more churn. other than that, the
largest change was removing the now-useless Services.jsm workaround as
well as removing globalGetters for objects already loaded automatically.

[1]: https://hg.mozilla.org/mozilla-central/rev/68ba071ff6fb9978937496f9adc48e378957f594
[2]: bugzil.la/1881890