Adopt build repository

[maximiliantech]

Description

We have the https://github.com/openmcp-project/build repository to reuse common workflows and CI stuff across all our repos using Taskfiles.

Task

• Adopt build repository at metrics-operator

Acceptance Criteria

• Operator is using Taskfile
• .github/workflows/... files match the overall structure with the rest of the org
• linux/amd64 and linux/arm64 images are available in GHCR

[maximiliantech]

Currently, we are just building and pushing the image for linux/amd64.

❯ docker pull ghcr.io/openmcp-project/github.com/openmcp-project/metrics-operator/images/metrics-operator:v0.6.1
v0.6.1: Pulling from openmcp-project/github.com/openmcp-project/metrics-operator/images/metrics-operator
no matching manifest for linux/arm64/v8 in the manifest list entries

This seems to be caused by a wrong configuration in our repo setup. Let's keep track of that in the acceptance criteria.