Review Mozilla 1946569: Wait for New Tab built-in addon to be enabled before allowing navigations to about:home and about:newtab to complete

🔍 Bugzilla Audit

Bugzilla: https://bugzilla.mozilla.org/show_bug.cgi?id=1946569

Description

Part 2 patch in this bug moved the code we change in function AboutRedirector::NewChannel from file browser/components/about/AboutRedirector.cpp to file browser/components/newtab/AboutNewTabRedirector.sys.mjs.

The change is non trivial, therefore the code was not moved in the 138 rebase where the change happened. We need to figure out how and make the change to browser/components/newtab/AboutNewTabRedirector.sys.mjs.

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