One AArch64 port, not two

Until version 12, JDK had two 64-bit ARM ports, even though both produce an AArch64 implementation. As a maintenance feature, this JEP removes all sources related to the 64-bit 64-bit ARM platform and retains the 64-bit ARM AArch64 port. It will prevent the duplication of work to maintain two ports. As part of the process, the option to build this port will also be removed from JDK. It will also validate that the 32-bit ARM port continues to work as expected and that it isn't affected by these changes.