runtime: Refactor asm_support to be auto-generated (mostly)

Usage:

* If the defines are no longer up to date, re-run generate-asm-support

* To add a new field:
--- Edit one of the offset_ or constant def files.
--- Rebuild cpp-define-generator and re-run generate-asm-support

Change-Id: I772430fcf1ad9af40898ebb453848f8412612386
TODO: Integrate this into the build somehow
TODO: Account for 32 vs 64-bit and read barrier vs no read barrier