Don't require BLK nodes for SIMD

Don't require BLK nodes for SIMD

Eliminate most cases where an OBJ or BLK node is required for SIMD
values. The exception is the case where a value produced by an intrinsic
(SIMD or HWIntrinsic) is used as an argument but the argument is of a
different SIMD type (e.g. a different baseType),

Commit migrated from https://github.com/dotnet/coreclr/commit/d57aca4b2f64942724bbfc0e40db6a125848df47