Add compile-only CI coverage for the parked Flink 1.18 through 2.0 modules

#19514 leaves a single Flink lane, so the Flink 1.18, 1.19, 1.20 and 2.0 datasource modules are not compiled by any job. A shared-code change that builds against the surviving version can break them on master undetected.

A cheap compile-only lane per version would close the gap without paying for the test suites. Full test coverage can come back later as the runner budget allows.

Part of #19524.

Start by comparing the surviving Flink CI lane with the parked Flink 1.18, 1.19, 1.20, and 2.0 modules. Identify the existing CI configuration entry points for that lane, then add one compile-only job per version; done means each module is compiled in CI without running its test suite.

Written by the indexing model from the issue text.