Changed default gatling image

[yokawasa]

Description

Changed default gatling image

Before: denvazh/gatling:latest After: ghcr.io/st-tech/gatling:latest

The new image is built with our managed files placed under gatling-operator/gatling, and it's Dockerfile is fully based upon denvazh/gatling:3.2.1.
In the future, we'll optimize gatling image and push it to our registry path

In addition, I've updated sample manifests, the CRD types comment, CRD, and relevant api docs as well

• config/samples/gatling-operator_v1alpha1_gatling01.yaml
• config/samples/gatling-operator_v1alpha1_gatling02.yaml
• docs/api.md
• api/v1alpha1/gatling_types.go
• config/crd/bases/gatling-operator.tech.zozo.com_gatlings.yaml

Test

I've deploy the new gatling operator and deploy Gatling CR whose gatling image is ghcr.io/st-tech/gatling:latest. I confirmed that the gatling scenario has run as expected.

make kind-deploy
make sample-deploy SAMPLE_IMG=ghcr.io/st-tech/gatling:latest

[yokawasa]

All reviewers Thanks for the review! I'm going to merge this