x86 NCG SIMD: Implement pack/insert/broadcast/unpack for integer vectors
## Motivation
Support of integer vectors in NCG would be nice.
As a start, I'd like to implement non-arithmetic basic operations (pack/insert/broadcast/unpack) on integer vectors.
## Proposal
Implement pack/insert/broadcast/unpack for `Int8X16#`, `Word8X16#`, `Int16X8#`, `Word16X8#`, `Int32X4#`, `Word32X4#`, `Int64X2#`, `Word64X2#` in x86 NCG.
Some of them (64X2) are already implemented in !12857/!12860, but they could be enhanced to use SSE4.1 instructions if enabled.
See also #25030.
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