Move arm64 insOpts entries into insScalableOpts (dotnet#96692)

* Move arm64 insOpts entries into insGroupOpts

insOpts has a max size of 6 bits, and it is getting full.

For some of the options, they are only required to specify the
encoding group, after this only the lane size (_S etc) is needed.
Move these to a new enum insGroupOpts.

* Nits

* Rename to insScalableOpts

* Remove _WITH_SIMD_VECTOR

* Remove _WITH_PREDICATE_MERGE. Reuse _idReg3Scaled.

* Remove insOptsScalableSimple

* Better insScalableOpts entry names

* Add INS_SCALABLE_OPTS_NONE asserts

* Remove INS_SCALABLE_OPTS_WITH_SCALAR

* insScalableOpts descriptions

* Remove uses of INS_SCALABLE_OPTS_WITH_SIMD_SCALAR for single variants

* Remove unused sopt from emitIns_R_R

* Add insScalableOptsNone

* Restore unreached() for capstone unsupported

* Add insOptsScalableStandard