Build multi-arch images

[glebiller]

Changes

Changed Dockerfile & Makefile to build a multi-platform (amd64 and arm64) image of jenkins-operator.
Using TARGETOS and TARGETARCH in the builder and leverage docker build build command in the Makefile.

💥 Breaking changes 💥
It is required to run docker buildx create --use before being able to create & push the image to registry.
Currently podman does not support buildx features, this changes requires CONTAINER_RUNTIME_COMMAND=docker.

🧪 Unit tests changes 🧪
Fixing unit tests with the following changes:

• reduce Jenkins CPU requirements from 1 to 250m
• upgrade Jenkins image to jenkins/jenkins:2.319.3-lts

Release Notes

Support multi-arch (amd64 and arm64) container image.

Upgrade base plugins to following versions:
* configuration-as-code: v1346.ve8cfa_3473c94
* git: 4.10.3
* job-dsl: 1.78.1
* kubernetes: 1.31.3
* workflow-job: 1145.v7f2433caa07f

[glebiller]

I am still investigating why there is a timeout when running e2e tests.
It looks like the operator running cannot access minikube through its public IP 192.168.49.2 :(

[bhubert]

you should add the plateform to the tag name, something like
--tag $(DOCKER_REGISTRY):$(GITCOMMIT)-$* . \

[glebiller]

/assign @Sig00rd
By bumping the Jenkins version & changing the default version of Plugins to match the one installed by a standard install, all the e2e are now passing correctly, in addition to building the ARM version of the image :)

[Sig00rd]

Thanks @glebiller, great work!