ASM kernels: remove v2 metadata

[averinevg]

This PR removes code object v2 metadata support from ASM kernels.

[averinevg]

@atamazov Please review

[atamazov]

@atamazov Please review

@averinevg I would prefer keeping this v2 code (albeit unused) until we add support for v4 or v5. Why: existing code works as a hint -- it denotes all places where conditional assembly might be needed to support some new MD format. What do you think?

[averinevg]

@atamazov Sounds reasonable. We'll probably need to add metadata for PAL runtime, then this code will come in handy