sys/amd64/conf: unify MINIMAL and GENERIC debug

[llfw]

Add debugging features (WITNESS, INVARIANTS, etc.) to MINIMAL to match the options enabled in GENERIC.

Add a new MINIMAL-NODEBUG kernel which turns these features off in the same way GENERIC-NODEBUG does.

This reduces the differences between GENERIC and MINIMAL in a way that should be less confusing to users.

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this only addresses amd64 for now. other archs can have the equivalent changes made afterwards if this causes no issues.