Make ByteBuddyDoFnInvokerFactory injection strategy configurable + drop the singleton

org.apache.beam.sdk.transforms.reflect.DoFnInvokers + DoFnInvokerFactory design is to be a SPI to let user plug their own bytecode manipulation library, however in practise beam uses ByteBuddyDoFnInvokerFactory as a singleton which makes all this design useless.

ByteBuddyDoFnInvokerFactory is also not configurable at all - typically the injection strategy so it assumes it runs in an environment and on a JVM where it will work - it does not on java 11 for instance.

This ticket is about fixing all these small inconsistency and blocker to tun on java 11.