Separate playwright deps into a dedicated tag

[AdrienClairembault]

Split playwright into a separate tag so we don't include 400mb of dependencies into the base image.

This will speed up CI jobs that do not need them as the image will be much lower to download (the size is reduced by almost half).

No changes for the plugin CI (it will use the playwright variant so we are sure to not break them, the plugins maintainers can make another PR later if they wish to benefit from it).

For the core CI, I guess it will go red once we merge this for the e2e step but we can update it quickly after.

[AdrienClairembault]

I think the CI failures are expected here?

[froozeify]

Not totally certain by looking at the outpute errors :

 - InvalidDefaultArgInFrom: Default value for ARG $BASE_IMAGE results in empty or invalid base image name (line 3)
Dockerfile:3
--------------------
   1 |     ARG BASE_IMAGE
   2 |     
   3 | >>> FROM $BASE_IMAGE
   4 |     
   5 |     LABEL \
--------------------
ERROR: failed to build: failed to solve: ghcr.io/glpi-project/githubactions-php-apache:8.5-playwright: failed to resolve source metadata for ghcr.io/glpi-project/githubactions-php-apache:8.5-playwright: ghcr.io/glpi-project/githubactions-php-apache:8.5-playwright: not found

I assume it's because the first image isn't build/publish yet