egl: move fallback calls to eglapi.c (2nd attempt)
!87 (merged) was missing a hunk in one of the commits; I reverted it, and this is the 2nd attempt, hopefully without any issues.
I'm doing the moves one at a time now, so as to avoid the mistake from last time.
Pending CI run will be here:
https://mesa-ci.01.org/eric_engestrom/builds/101/group/63a9f0ea7bb98050796b649e85481845
/cc @tpalli @evelikov @cmarcelo @craftyguy