Draft: bug_34108+40266+25934+40251+40259+40272: Update components for switch to mozilla88-based Fenix (+ other changes)

Closes #25934 (closed) #40251 (closed) (reviewed in !253 (closed))

Closes #34108 (closed) #40266 (closed) (same patches as in !259 (closed), but with an issue fixed: we were redefining the steps section in projects/geckoview/config and losing the merge_aars step)

Closes #40272 (closed).

Closes #40259 (closed).

Still a draft: #40259 (closed) is not complete.

This is replacing !260 (closed).