cpu-features: Update OS queryable hwcaps (#43)

* cpu-features: Support hwcap for FEAT_MTE3
* cpu-features: Support hwcap for FEAT_SME
* cpu-aarch64: Allow specifying IDRegister field size
This will be necessary for testing some SME extensions.

Preserves existing behavior by defaulting the field size to 4 bits.

* cpu-aarch64: Add skeleton for AA64SMFR0_EL1
This register contains the bulk of the SME extension bitfields.

* cpu-features: Support hwcap for FEAT_SME_I16I64
* cpu-features: Support hwcap for FEAT_SME_F64F64
* cpu-features: Support hwcap for FEAT_SME_I8I32
* cpu-features: Support hwcap for FEAT_SME_F16F32
* cpu-features: Support hwcap for FEAT_SME_B16F32
* cpu-features: Support hwcap for FEAT_SME_F32F32
* cpu-features: Support hwcap for FEAT_SME_FA64

* cpu-aarch64: Handle hwcap auxvals separately
HWCAP2 makes use of bit 31 and bit 32 which would fall outside the range
of what can be handled by one array, so we can split the array into two
arrays and combine over them individually.

* cpu-features: Support hwcap for FEAT_WFxT
* cpu-features: Support hwcap for FEAT_EBF16