Move git clone openj9 repo in functional level

Currently, we do git clone openj9 repo (in [get.sh](https://github.com/adoptium/aqa-tests/blob/fe5b09797f2ea602cc5457784e0f5d43d8102507/get.sh#L494-L541)) regardless of what type of tests we run. We did this because TKG was in openj9 repo and we need to get TKG for running tests. With TKG separated out the of openj9 repo, we should move git clone openj9 repo in build.xml under functional dir https://github.com/adoptium/aqa-tests/tree/master/functional. That is, only git clone openj9 repo if we run functional tests. This would simplify the process and reduce testing overhead.

Inspect get.sh lines 494-541 and the build.xml entry under functional to understand the current clone flow and functional-test setup. Move the OpenJ9 clone so functional tests still obtain it, while other test types no longer perform the clone; verify both paths through the existing test invocation flow.

Written by the indexing model from the issue text.