Add more repeat support and register views.

Rationale:
This enables exhaustive testing of instructions
that use various memory addressing modes and
register views (full, half, quarter, etc.).

Bug: 18380245
Bug: 18380559
Bug: 18380348

Test: assembler_x86[_64]_test
Change-Id: I598c3e35a4791166ab629479ccb969ef3c6494b8