Remove os-specific information

[rhelmot]

Description

Over the years, archinfo has been abused to store information which is not universal to the architecture. The prime example of the problem is arch.syscall_num_offset. This is linux-specific, and even ABI specific!

Alternatives

No response

Additional context

No response

[twizmwazin]

@rhelmot, where do you think this information would be better put?

[rhelmot]

At the very least, in a name which indicates the specific domain of its usefulness. This was the plan for the original feat/plugins branch, but we all know how well that went.