Various improvements to interpreter.

- Created separate Next_xxx methods to get the next instruction to
  avoid having to look up the size based on the opcode.
- Moved exception handling to after throwing instructions only.
- Added a test of all thread flags before checking for suspend during
  the interpreter execute loop.
- Made it unlikely that instrumentation has dex pc listeners for
  DexPcMovedEvent.

Change-Id: I88afc98cf42f2e36c747582df8e74669d24ef864