Use digest for sqlserver and fix tests

[joperezr]

An update to mssql/server image tag 2022-latest broke our tests as we can no longer communicate with the container. Chatting offline with our experts from the dotnet-docker repo, they suggested we should instead depend on digests as opposed to tags, to be able to guarantee determinism, and then just make sure we update these digests in a frequent basis to ensure we get fixes for them. This PR is switching just the sqlserver hosting component to use digest instead and it also does that for the tests so that they pass again, but we will likely want to make an overhaul pass to all of our hosting components to similarly depend on digests as opposed to tags.

cc: @mitchdenny @radical @eerhardt

Microsoft Reviewers: Open in CodeFlow

[eerhardt]

they suggested we should instead depend on digests as opposed to tags, to be able to guarantee determinism

Note that this is OK to unblock our tests, but this doesn't comply with our long term plan.

#3933
#1997 (comment)

This approach doesn't allow for security patches to be automatically applied.

[joperezr]

Let's have a follow up discussion just to finalize on our plan going forward. We may very well end up following the same plan we have, I just want to make sure we take into consideration the concept of determinism and the fact that we have now been broken by this, so we should check what our customers would expect us to do.

For this particular case, it's worth noting that the underlying image doesn't follow semver which seems to be one of the keys of our plan.

[joperezr]

Closing in favor of #5058 where @radical was able to keep the tests enabled without the need to use digests. We should still figure out how to fix this not only for our tests, but also for our hosting component.