x86/gen-cpuid: Rework internal logic to ease future changes

x86/gen-cpuid: Rework internal logic to ease future changes

Better split the logic between parse/calculate/write.  Collect the feature
comment by their comment character(s), and perform the accumulation operations
in crunch_numbers().

Avoid rendering the featuresets to C uint32_t's in crunch_numbers(), and
instead do this in write_results().  Update format_uint32s() to call
featureset_to_uint32s() internally.

No functional change - the generated cpuid-autogen.h is identical.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>