Arm64 HWIntrinsics: Tests for Immediate methods should test with non-constants

[a74nh]

There are many APIs with "constant expected" arguments.

eg:

(Vector128<sbyte> Value1, Vector128<sbyte> Value2) LoadAndInsertScalar((Vector128<sbyte>, Vector128<sbyte>) values, [ConstantExpected(Max = (byte)(15))] byte index, sbyte* address)

There are a lack of tests to test passing a non-constant value into the method:
eg: we test LoadAndInsertScalar(vectorx, 3, addr); but not LoadAndInsertScalar(vectorx, inty, addr);

In addition, many of the constant values tests use values hardcoded into the script. We have ways of randomly generating values and should do that instead.

[dotnet-policy-service]

Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch
See info in area-owners.md if you want to be subscribed.