Run unit tests with vips as the driver for intervention/image

[GuySartorelli]

osiemsiedem/intervention-image-vips-driver provides a driver for libvips, which is a more efficient alternative to GD and Imagick for manipulating images.

There have been PRs in the past to allow libvips to work with Silverstripe CMS - but we don't run tests against it, so regressions could sneak in.

Getting libvips driver working

1. Install libvips (e.g. sudo apt install libvips42)
2. Add osiemsiedem/intervention-image-vips-driver (e.g. composer require osiemsiedem/intervention-image-vips-driver)
3. Configure the libvips driver for intervention/image via yaml config:

   SilverStripe\Core\Injector\Injector:
     Intervention\Image\ImageManager:
       constructor:
         - { driver: Vips }

Acceptance criteria

• An additional job is added to CI for this module which runs the unit tests with libvips configured as the driver for intervention/image

[maxime-rainville]

We had some initial discussion with CreMarketing about this.

Vips looked like it could in theory be quite a cool improvement for generating images. Our own testing has been a bit more dubious.

Intervention 3 doesn't support it and doesn't seem inclined to support it. This would be a blocker for CMS 6 support.

Validation required:

• What are the scenarios where this could be beneficial?
• Could this be supported on SC?