Scoped ByteBuffer vector access

The Foreign Memory API supports viewing a MemorySegment as a ByteBuffer, an instance of which can then be passed to the vector load/store access methods.

Such ByteBuffer access requires accesses are scoped (a method annotated with ScopedMemoryAccess.Scoped) and the ByteBuffer's scope (instance of ScopedMemoryAccess.Scope) checked for validity. Thereby ensuring exceptional failure if a shared buffer has been closed.