streamingccl: multi-node unit tests

[samiskin]

None of our tests used to run with multiple nodes and a scattered table, so this PR re-enables the unvavailable node test and creates a new basic multinode test.

Release note: None

[cockroach-teamcity]

This change is 

[samiskin]

@gh-casper The issue didn't end up happening anymore, at least not like it used to, so I think it was somehow fixed by one of the PRs that were in flight at the time. The only bug fix here was around the creation statement being retried, added that to the description now :+1:

It's likely that https://github.com/cockroachdb/cockroach/pull/85866 was the issue I was seeing during the roachprod demo.

[samiskin]

bors r+

[craig[bot]]

Build failed:

• Bazel Essential CI (Cockroach)

[samiskin]

bors r+

[craig[bot]]

Build succeeded:

• Bazel Essential CI (Cockroach)