Support OPENJCEPLUS_GIT_REPO and OPENJCEPLUS_GIT_BRANCH in testenv.properties

[llxia]

openJcePlusTests under https://github.com/adoptium/aqa-tests/tree/master/functional/OpenJcePlusTests (the test material is from https://github.com/ibmruntimes/OpenJCEPlus.git) has a close tie with Semeru release. Using incompatible test material could lead to the failure of release testing, resulting in unnecessary delays. Therefore, AQA test repo needs to track OPENJCEPLUS_GIT_REPO and OPENJCEPLUS_GIT_BRANCH for each Semeru release.

We should support OPENJCEPLUS_GIT_REPO and OPENJCEPLUS_GIT_BRANCH in testenv.properties, so we have a fixed version of test material for the release testing. Similar to openjdk, openj9, TKG, system test repos in testenv.properties file. It also means that we will support branch, tag, or SHA in OPENJCEPLUS_GIT_BRANCH value.

[llxia]

FYI @pshipton @jasonkatonica @smlambert