[FMV] Remove features which can be expressed as a combination of other features

[labrinea]

All of sve-bf16, sve-ebf16, and sve-i8mm are obsolete. This is already reflected on the second column of the FMV table (we have bf16, ebf16, and i8mm with the same Architecture name).

According to https://developer.arm.com/documentation/ddi0487/latest Arm Architecture Reference Manual for A-profile architecture:

D23.2.72 ID_AA64ISAR1_EL1, AArch64 Instruction Set Attribute Register 1

ID_AA64ISAR1_EL1.I8MM, bits [55:52]

When Advanced SIMD and SVE are both implemented, this field must return
the same value as ID_AA64ZFR0_EL1.I8MM

ID_AA64ISAR1_EL1.BF16, bits [47:44]

When FEAT_SVE or FEAT_SME is implemented, this field must return the
same value as ID_AA64ZFR0_EL1.BF16.

So one could write target_version("sve+bf16") or sme+bf16 instead.

There is a proposal to explicitely document FMV feature dependences in ACLE, so that the user won't have to write long feature strings on the attributes like sve+simd+i8mm (sve+i8mm should be enough).

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[labrinea]

@tmatheson-arm

[labrinea]

Adding @andrewcarlotti and @DanielKristofKiss for visibility

[andrewcarlotti]

LGTM

[labrinea]

@vhscampos I accidentally closed this before it got merged. Can you take a look?