e2e tests: Containerfile presence

[slimreaper35]

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[slimreaper35]

Are you okay with this change?
In the future, when creating new e2e tests, part of the repo can / should be Containerfile, too.

I think it will make life easier when testing locally. Also, I suppose users have their Containerfile in the same repo when using cachi2.

[eskultety]

While I appreciate you're thinking of doing this in a compatible manner, it's actually going to lead to a very messy state where part of the tests will have the containerfile inside the e2e repo and the rest will have it in cachi2 integration test data. I'd prefer if this was proposed as a complex change == move the existing container files out of cachi2 and mandate that new e2e repos follow the proposed practice. Which brings me to #430 which this change would be nicely paired with that docs where this practice would be explained.