[Docker] Switching to buster php build (#5589)
[Docker] Switching to buster php build (#5589)

PHP has now has new builds with buster bases.
Docker file has been changed to use those builds instead of stretch.
While I was in there, I also made a cheeky little xdebug update to latest.


This build has been tested with 2 bigger projects of mine, one is lower level (API), and the other is e2e (selenium) based.
Both seemed to be fine without any further changes.
Naktibalda/Codeception,Codeception/base,Codeception/Codeception,Codeception/base,Codeception/Codeception,Naktibalda/Codeception,Codeception/base,Naktibalda/Codeception