efl: Remove cserve2 support

Summary:
As cserve2 support has not worked (if ever) in a very long time, and
it's authors are gone, this series of patches removes cserve2 (and
thus cache2) from our codebase to remove cruft and reduce
maintainability of unused code.

ref T7226
Depends on D6941

Reviewers: raster, cedric, zmike, Hermet

Reviewed By: Hermet

Subscribers: reviewers, committers

Tags: efl

Maniphest Tasks: T7226

Differential Revision: https://phab.enlightenment.org/D6942