Remove GT_ADDEX and replace with more generalized containment handling (#76273)

Remove GT_ADDEX and replace with more generalized containment handling (#76273)

* Remove GT_ADDEX and replace with more generalized containment handling

* Handle small types for (extended register) instructions

* Remember to handle IsRegOptional

* Applying formatting patch

* Preference containing the CAST of `ADD(op1, CAST(op2))` rather than the op2 of CAST

* Update src/coreclr/jit/lowerarmarch.cpp

* Adding a test covering the caught fuzzlyn scenario

* Ensure the new test returns 100

* Skip a Fuzzlyn generated regression test on Mono wasm/llvmaot/llvmfullaot