[X86][AMX] combine tile cast and load/store instruction.

The `llvm.x86.cast.tile.to.vector` intrinsic is lowered to
`llvm.x86.tilestored64.internal` and `load <256 x i32>`. The
`llvm.x86.cast.vector.to.tile` is lowered to `store <256 x i32>` and
`llvm.x86.tileloadd64.internal`. When `llvm.x86.cast.tile.to.vector` is
used by `store <256 x i32>` or `load <256 x i32>` is used by
`llvm.x86.cast.vector.to.tile`, they can be combined by
`llvm.x86.tilestored64.internal` and `llvm.x86.tileloadd64.internal`.

Differential Revision: https://reviews.llvm.org/D124378