feat: add image-keep option for built images

[lefinal]

What does this PR do?

Adds an option to keep images if they have been built.
This avoids the need to build these images every time from scratch.
Built images are being kept in DockerContainer.Terminate when KeepImage is set to true in ContainerRequest.

Why is it important?

If images for testing are built with long build time, they are currently always deleted.
This means that for each test run, the whole image needs to be rebuilt.
If the image stays the same for every test, this may take up a lot of time.

Related issues

• Relates [Enhancement]: Cache FromDockerfile builds to allow multiple containers using the same image #1485

How to test this PR

Create a container with image-build manually and set KeepImage to true.
Tests for this functionality have been added as well.

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[mdelapenya]

I added a few comments that need to be addressed. But other than that, this LGTM.

Once resolved I think we can merge this one, thanks for your contribution!

[mdelapenya]

@lefinal I'm planning a release hopefully this week, so I took this PR and fixed the lint for you (running make lint from root of the project).

Regarding my comments regarding coding style, are you interested in updating the PR with them? I can do it myself on top of your commits in order to have this PR in the new release

[lefinal]

@lefinal I'm planning a release hopefully this week, so I took this PR and fixed the lint for you (running make lint from root of the project).

Regarding my comments regarding coding style, are you interested in updating the PR with them? I can do it myself on top of your commits in order to have this PR in the new release

I made the requested changes. Do you want me to squash them so that we have a clean history? Or are the 5 commits okay. Don't know if you generate any changelogs from them.

[mdelapenya]

I made the requested changes. Do you want me to squash them so that we have a clean history? Or are the 5 commits okay. Don't know if you generate any changelogs from them.

Thanks for doing it! No worries, we always squash the PRs when merging them into main. Will trigger the CI (it will pass, I ran your tests locally and they pass) and merge the PR.

[mdelapenya]

LGTM! Thanks for taking the time to contribute this feature.