TBA Alpha fails to initialize WebExtensions

This is one of the causes of #44398 (closed).

I've found it affects any add-on (tested with uBlock Origin), may be due to a 147-specific upstream bug, not identified yet, and/or to some of our modification.

Either way, at least NoScript (because made persistent, as a partial fix to #44398 (closed)), once it manages to run it keeps going through the whole session - as it's always the case when it gets installed on first startup, or it gets manually restarted from a debugging session.

Same goes for uBlock Origin when you disable and re-enable it from the UI (which is hidden in NoScript's case).

Therefore as a temporary work-around (the bug might be already fixed in 148, otherwise we should find what's wrong with our specific setup), I'd suggest to iterate through all the installed extensions (WebExtensionsRuntime.listInstalledExtensions()) and disable/enable those which are found already enabled (WebExtensionsRuntime.enableWebExetension()) in TorBrowserFeature.install().

/cc @clairehurst, @dan

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