use JBTIS style of TP merging for JBT Central and Early Access TPs, in order to reduce dupe entries in the TPs

As discovered in JBIDE-17519, both the JBT Central and new JBT Early Access target platforms cannot be fully resolved on disk due to missing dependencies.

So, rather than iteratively sticking all the individual IUs (over 100 and counting) into the .target files, which duplicates what's already in the upstream TPs, we should instead use the JBTIS style of .target file merging for JBT Central and Early Access.

This will reduce duplication, allow the new verifyTarget.sh to work on local changes to the target platform definitions, and make TP maintenance easier.