Add a "readiness probe" to DIND in CI

Relates to https://repo1.dso.mil/platform-one/big-bang/bigbang/-/issues/187

This is a solution for the bullet 2 in that issue. It uses a basic bash script found in an upstream issue that will wait on DIND to be available before proceeding (or fail after a minute). This is required because upstream gitlab runners do not yet provide a way to specify readiness probes to the services used (see this issue as well as others upstream).

This is a "sister" to the BB pipeline fix - https://repo1.dso.mil/platform-one/big-bang/bigbang/-/merge_requests/702