Add parent pom for int tests

The integration test projects need to be built in a particular order, however they are specified as unrelated POMs.

The first compile step (and later, in the SAST steps) the CI/CD pipeline will attempt to build all of these. However, without any ordering information, it doesn't do it in the correct order (incidentally, it uses alphabetic order, and therefore runs search-test-aws before search-test-core; creating a problem).

This MR adds an extra pom at the integration testing layer, which specifies the build order of the various components. Note: The CI/CD pipelines will notice that the search-test-X projects are child projects and not attempt to build them individually. Instead, it will build only the two parent projects.

This strikes a balance between being low impact -- the integration testing build projects are still separated and not part of the main build environment -- and not requiring complex logic in the pipelines to scan for dependencies. The main project still needs to be built first, and that is not specified in any POM, but the CI/CD pipelines always build the parent POM first as a rule, so we rely on that rule here.