WIP: Bug 34432

This request is about merging the fixes to the 16 child tickets mentioned in #34432 (closed). That should allow us to keep both the new toolchain and the older ones on tor-browser-builds master and make progress on building a Fenix-based Tor Browser.

To test the changes I pushed bug_34432_v3_test with an additional commit to pick up a rebased GeckoView branch. Using that branch running

./rbm/rbm build fenix-tor-android-service --target torbrowser-testbuild --target torbrowser-android-fenix-armv7 (replace "armv7" for the other architecture)

and

./rbm/rbm build geckoview --step merge_aars --target torbrowser-testbuild --target torbrowser-android-all

should build everything for that is getting changed for Fenix.

Compared to the previous review done by @ahf I needed make 4 smaller and larger changes (IIRC):

1. Node has a newer version now (10.21)
2. I found a bug in cbindgen I fixed
3. I needed to adjust things for the fenix- namespace where required, so we can keep everything on master
4. I needed to take upcoming changes for application-services into account as that project requires a newer NDK (r21).