[RyuJIT Wasm]: Fix incorrect assert for shift amount type in codegenwasm.cpp

[adamperlin]

Fixes #129263; This came up due to the following IL in a regression test:

 ldc.i8 0xa60d377f2863e61c
 ldsflda unsigned int16 ILGEN_0x3c109d11::field_0x1
 ldind.u2
 shr.un

We have a load of a ushort as the shift operand, and this is preserved through import down to codegen.
We were asserting that the exact type for the shift amount operand is TYP_INT, when this may not be the case since the shift amount could be a smaller integer type that still fits in TYP_INT. Instead, the assert should use genActualType

[Copilot]

Pull request overview

This PR adjusts a debug assertion in the Wasm RyuJIT code generator so that 64-bit shift/rotate nodes accept shift-amount operands whose actual type is TYP_INT, even when the operand’s node type is a smaller integral type (e.g., TYP_USHORT).

Changes:

• In CodeGen::genCodeForShift, replace the strict TypeIs(TYP_INT) check on the shift amount with an genActualType(... ) == TYP_INT check for TYP_LONG shifts/rotates.

[AndyAyersMS]

Fix up the comment and we're good.

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