Arm64 SVE: Rename Prefetch APIs names to use Bit

[a74nh]

The following Prefetch APIs were implemented:

public static unsafe void GatherPrefetch8Bit(Vector<T> mask, Vector<T2> addresses, [ConstantExpected] SvePrefetchType prefetchType);
public static unsafe void GatherPrefetch8Bit(Vector<T> mask, void* address, Vector<T2> offsets, [ConstantExpected] SvePrefetchType prefetchType);
public static unsafe void GatherPrefetch16Bit(Vector<T> mask, Vector<T2> addresses, [ConstantExpected] SvePrefetchType prefetchType);
public static unsafe void GatherPrefetch16Bit(Vector<T> mask, void* address, Vector<T2> indices, [ConstantExpected] SvePrefetchType prefetchType);
public static unsafe void GatherPrefetch32Bit(Vector<T> mask, Vector<T2> addresses, [ConstantExpected] SvePrefetchType prefetchType);
public static unsafe void GatherPrefetch32Bit(Vector<T> mask, void* address, Vector<T2> indices, [ConstantExpected] SvePrefetchType prefetchType);
public static unsafe void GatherPrefetch64Bit(Vector<T> mask, Vector<T2> addresses, [ConstantExpected] SvePrefetchType prefetchType);
public static unsafe void GatherPrefetch64Bit(Vector<T> mask, void* address, Vector<T2> indices, [ConstantExpected] SvePrefetchType prefetchType);

public static unsafe void Prefetch8Bit(Vector<T> mask, void* address, SvePrefetchType op); // PRFB
public static unsafe void Prefetch16Bit(Vector<T> mask, void* address, SvePrefetchType op); // PRFH
public static unsafe void Prefetch32Bit(Vector<T> mask, void* address, SvePrefetchType op); // PRFW
public static unsafe void Prefetch64Bit(Vector<T> mask, void* address, SvePrefetchType op); // PRFD

However, the last four were implemented as:

public static unsafe void PrefetchBytes(Vector<T> mask, void* address, SvePrefetchType op); // PRFB
public static unsafe void PrefetchInt16(Vector<T> mask, void* address, SvePrefetchType op); // PRFH
public static unsafe void PrefetchInt32(Vector<T> mask, void* address, SvePrefetchType op); // PRFW
public static unsafe void PrefetchInt64(Vector<T> mask, void* address, SvePrefetchType op); // PRFD

Original API reviews: #97831 and #94007

Either the Prefetch*() APIs or the GatherPrefetch*() APIs need renaming.

[dotnet-policy-service]

Tagging subscribers to this area: @dotnet/area-system-runtime-intrinsics
See info in area-owners.md if you want to be subscribed.

[tannergooding]

From what I recall from API review, the #bit names were intentional so we didn't need byte* and sbyte* variants.

The new names aren't really consistent either, as you have Bytes vs Int16 rather than Int16s (which doesn't flow well).

I'd say we should fix this back to match the originally approved APIs, unless someone has a better suggestion for the names to use.

[a74nh]

Switched the title and description so that it's no longer an API suggestion change