arm64: Refactor mov/movprfx for unmasked operations

[ylpoonlg]

This PR is the first of a few contributing to #115508.

• Apply the proposed changes to the codegen and emit functions for the non-embedded masked operations, which only concern cases using unpredicated mov/movprfx.
• Clean up RMW instructions codegen in hwintrinsiccodegenarm64.cpp.
• Add a helper emit function to handle SVE mov/movprfx checks.
• Move the special codegen for AddCarryWideningEven/Odd into the emit function.

cc @dotnet/arm64-contrib @a74nh

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[ylpoonlg]

SPMI asmdiffs:

 G_M39772_IG02:        ; bbWeight=1, gcrefRegs=0000 {}, byrefRegs=0000 {}, byref
             ldr     q16, [fp, #0x20]	// [V00 arg0]
             ldr     w0, [fp, #0x1C]	// [V01 arg1]
-            mov     v0.16b, v16.16b
+            movprfx z0, z16
             insr    z0.s, w0
-						;; size=16 bbWeight=1 PerfScore 8.50
+						;; size=16 bbWeight=1 PerfScore 10.00

ASIMD movs are replaced with SVE movprfxs where possible. Slight increase in PerfScore, but this would allow the uarch to fuse them with the following instruction.
Other failures look unrelated.