roachtest: port smoketest/secure/multitenant to new APIs

[herkolategan]

See the parent issue [1] for details. Test location: pkg/cmd/roachtest/tests/smoketest_secure.go

[1] https://github.com/cockroachdb/cockroach/issues/115867

Epic: CRDB-31933

Jira issue: CRDB-35300

[blathers-crl[bot]]

cc @cockroachdb/test-eng

[renatolabs]

@herkolategan I think the right move is actually to delete the smoketest_secure.go file instead 😄

The tests in that file are very basic (to the extent that they shouldn't even be roachtests), and many other tests in the nightly suite should have failed if the functionality they test was not working.

Thoughts?