aarch64: Simplify feature definitions

Currently the aarch64-option-extensions.def entries, the
aarch64-cores.def entries, and the AARCH64_FL_FOR_* macros
have a transitive closure of dependencies that is maintained by hand.
This is a bit error-prone and is becoming less tenable as more features
are added.  The main point of this patch is to maintain the closure
automatically instead.

For example, the +sve2-aes extension requires sve2 and aes.
This is now described using:

  AARCH64_OPT_EXTENSION("sve2-aes", SVE2_AES, (SVE2, AES), ...)

If life was simple, we could just give the name of the feature
and the list of features that it requires/depends on.  But sadly
things are more complicated.  For example:

- the legacy +crypto option enables aes and sha2 only, but +nocrypto
  disables all crypto-related extensions, including sm4.

- +fp16fml enables fp16, but armv8.4-a enables fp16fml without fp16.
  fp16fml only has an effect when fp16 is also present; see the
  comments for more details.

- +bf16 enables simd, but +bf16+nosimd is valid and enables just the
  scalar bf16 instructions.  rdma behaves similarly.

To handle cases like these, the option entries have extra fields to
specify what an explicit +foo enables and what an explicit +nofoo
disables, in addition to the absolute dependencies.

The other main changes are:

- AARCH64_FL_* are now defined automatically.

- the feature list for each architecture level moves from aarch64.h
  to aarch64-arches.def.

As a consequence, we now have a (redundant) V8A feature flag.

While there, the patch uses a new typedef, aarch64_feature_flags,
for the set of feature flags.  This should make it easier to switch
to a class if we run out of bits in the uint64_t.

For now the patch hardcodes the fact that crypto is the only
synthetic option.  A later patch will remove this field.

To test for things that might not be covered by the testsuite,
I made the driver print out the all_extensions, all_cores and
all_archs arrays before and after the patch, with the following
tweaks:

- renumber the old AARCH64_FL_* bit assignments to match the .def order
- remove the new V8A flag when printing the new tables
- treat CRYPTO and CRYPTO | AES | SHA2 the same way when printing the
  core tables

(On the last point: some cores enabled just CRYPTO while others enabled
CRYPTO, AES and SHA2.  This doesn't cause a difference in behaviour
because of how the dependent macros are defined.  With the new scheme,
all entries with CRYPTO automatically get AES and SHA2 too.)

The only difference is that +nofp now turns off dotprod.  This was
another instance of an incomplete transitive closure, but unlike the
instances fixed in a previous patch, it had no observable effect.

gcc/
	* config/aarch64/aarch64-option-extensions.def: Switch to a new format.
	* config/aarch64/aarch64-cores.def: Use the same format to specify
	lists of features.
	* config/aarch64/aarch64-arches.def: Likewise, moving that information
	from aarch64.h.
	* config/aarch64/aarch64-opts.h (aarch64_feature_flags): New typedef.
	* config/aarch64/aarch64.h (aarch64_feature): New class enum.
	Turn AARCH64_FL_* macros into constexprs, getting the definitions
	from aarch64-option-extensions.def.  Remove AARCH64_FL_FOR_* macros.
	* common/config/aarch64/aarch64-common.cc: Include
	aarch64-feature-deps.h.
	(all_extensions): Update for new .def format.
	(all_extensions_by_on, all_cores, all_architectures): Likewise.
	* config/aarch64/driver-aarch64.cc: Include aarch64-feature-deps.h.
	(aarch64_extensions): Update for new .def format.
	(aarch64_cpu_data, aarch64_arches): Likewise.
	* config/aarch64/aarch64.cc: Include aarch64-feature-deps.h.
	(all_architectures, all_cores): Update for new .def format.
	* config/aarch64/aarch64-sve-builtins.cc
	(check_required_extensions): Likewise.

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