Create initial nightly build/publish workflow

[chainchad]

This creates and publishes a "nightly" build (in the form of a Docker image) from trunk for:

1. core
2. core + plugins
3. ccip

In the future, we'll create the builds only if certain pre-requisites such as ci-core.yml and integration-tests.yml workflows on the same commit are passing.

This uses a new reusable workflow which itself uses new actions:

1. build-push-docker
2. build-push-docker-manifest

These new actions give us the following features:

1. SBOM / provenance
2. Manifest signing
3. Multiple arch support (amd64/arm64) with a manifest creation (just refer to one tag and it will pull the right platform)
4. Each arch build runs on a respective runner of that type (e.g. arm64 builds on arm64 runners)
5. Complete GitHub Summary with image details
6. Consistent docker image tags. Specify type: pr, nightly, branch, tag and get a standardized/tagged image.

Once we get comfortable with this new workflow and its underlying actions, the goal would be to use this pattern for all builds on this (and other!) repos such as builds for PR's, tagged releases, and pushes to trunk.

[cl-sonarqube-production]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarQube