chore: update docker proxy URL

[matthewelwell]

Changes

Sibling PR to https://github.com/Flagsmith/flagsmith/pull/5255.

Update docker proxy URL to flagsmith.com domain to give us more control. Also completes the switch from scarf to reo. dev.

How did you test this code?

Verified that the following commands worked

# Pull a public image
docker pull docker.flagsmith.com/flagsmith/flagsmith

# Login via dockerhub credentials
docker login docker.flagsmith.com

# Pull a private image
docker pull docker.flagsmith.com/flagsmith/flagsmith-private-cloud

[matthewelwell]

So, the 'Lint & Test' workflow is failing (due to a timeout) on this PR, but I can't work out why.

I originally assumed that it was related to an issue with github accessing docker.flagsmith.com, but it seems not to be the case since the test workflow I added to prove that images from docker.flagsmith.com can be pulled in a github action here worked (well, at least the docker pull did). I also think that I'm overriding the repository URL as per the change in this commit to charts/flagsmith/ci/e2e-test-values.yaml.

So, I'm pretty stumped here.