Remove usage of Tekton resources

[SaschaSchwarze0]

Changes

Related to Remove usage of Tekton resources #696.

Reviewers can go through the changes by commit:

1. Extend deployment configuration to include template for Git step extends the deployment configuration with a template for a Git step. I chose JSON as serialization format as this is easier to provide as a one-liner in a deployment yaml. Once we switch to a ConfigMap, we can revisit how we store the data there. The image URL can be configured in the template but is also available as separate environment variable. That's needed as our release build sets only the image URL based on the git image that we build (in commit 5)
2. Add custom gomega matcher adds a Gomega matcher to check for an element in an array or slice to contain an item with a certain name, is used in the unit tests in the next commit.
3. Remove Git and Image resources, introduce common handling of sources, use results is the main code change. The resources are removed, results are added. I introduced a structure for our different source types so that as we evolve that, we have a nice structure in our source code. Remote artifacts were moved to sources/http to fit into that structure. The runtime image code was extended to correctly fill the image results in the same way as the Kaniko sample strategy (see commit 6).
4. Stop adding source secret to the service account stops adding the source secret to the service account as this is directly mounted by the previous commit.
5. Build git image as part of the release build extends our deployment with the environment variable for the git image in ko-style. In the release build, I had to workaround the ko limitation that only one image name can be specified (see comment in the file). I just notice that the release.sh here references the GIT_IMAGE environment variable, this is set in the Makefile in commit 7. @qu1queee please do not forget to create the git repository in quay as discussed, so that the image can be pushed by the build.
6. Update sample build strategies to write to results updates the sample build strategies to write the image sha and size where possible. The EP also suggests solutions for BuildKit and maybe Buildah, those strategies can be extended in a follow-on PR. I focused on those that already supported that feature plus Buildpacks where it is trivial to access the image SHA. The strategy changes also outline that less chown in prepare steps is necessary for non-root build strategies. Remaining is the chown for the Tekton home directory that we will get rid of once we also move away from the service account and creds-init for the output image credential.
7. Update integration test makes the necessary changes to the integration test cases and updates our CI to build the git image and load it into the KinD cluster.
8. Update documentation adds the two results that the build strategy author can use to the build strategy documentation. The authentication documentation is updated to remove the Tekton annotation as that is not needed anymore. I am also removing the link to Tekton's authentication documentation. There's nothing for our users to learn there and we evolve to our own secret handling anyway.
9. Update EP with information on how the non-root git clone is implemented updates the EP with information about how to the non-root Git clone is done, and adjusts some naming for the volume mount to prevent possible conflicts with what build strategy authors could use by using the shp- prefix there.

Submitter Checklist

• Includes tests if functionality changed/was added
• Includes docs if changes are user-facing
• Set a kind label on this PR
• Release notes block has been filled in, or marked NONE

Release Notes

Remove usage of Tekton's pipelines resources in favor of a shipwright-managed step to clone a Git repository, and Tekton results to store information such as Git commit SHA and image digest and size

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[HeavyWombat]

I have not finished the full PR yet. We were able to check on the CI parts, publishing and integration tests. However, there are already things I would like to start a discussion.

[qu1queee]

Adding some comments on my first review. I still need to understand the override on the previous implementation @otaviof had for spec.sources, and then all changes when generating the Task/TaskRun, plus strategy renames. So pls expect 2 more reviews.

[qu1queee]

Next round of request for changes. Looks good in general, nice work!

[HeavyWombat]

/lgtm

[qu1queee]

/approve

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: qu1queee

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