fixup! Modify Add-on support (fixes fenix#40255)

• This fixup registers NoScript for automatic updates (a step missing from the original commit) on first install and on every startup, since if it had already been installed by a previous Tor Browser version it wouldn't get any update otherwise (if it's already registered this a NOP).
• We also try to upgrade NoScript to latest available stable version on first browser installation.
• References to the addonManager and addonUpdater components are deferred to onTorConnect() in order to prevent premature instantiation and network activity attempts, which would fail.
• Additionally we temporarily drop and restore the current thread policy while copying the XPI to cacheDir, because disk writing caused a crash on startup.

fixes #40225 (closed)