Bug 42018: Rebase to 115.2.1

Rebased our fork on top of upstream 115.2.1.

I've squashed everything since it was the first release anyway.

Closes tor-browser#42018 (closed).

/cc @richard

requested review from @dan

assigned to @pierov

changed the description

were you able to compile this? I'll try and give it a go and confirmation test this afternoon

does android-components/plugins/dependencies/src/main/java/Gecko.kt need to have version updated to "115.1.20230710165010"? it was unhappy for me with "115.0.20230710165010"

builds and works

approved this merge request

resolved all threads

merged