[RyuJit/WASM] Reach the NYI in genFnProlog

[SingleAccretion]

Pulling on the thread of NYIs a bit further. We now have this for my Problem(int a, int b) => a + b;:

Scope info: begin block BB01, IL range [000..004)
Added IP mapping: 0x0000 STACK_EMPTY (G_M56520_IG02,ins#0,ofs#0) label
Generating:                [000004] -----------                            IL_OFFSET void   INLRT @ 0x000[E--]
Generating: N001 (  1,  1) [000000] -----+-----                    t0 =    LCL_VAR   int    V00 arg0         u:1 (last use) $80
Mapped BB01 to G_M56520_IG02
IN0001:             i32.load 1 4
Debug: Closing V00 debug range.
                                                        Live vars after [000000]: {V00 V01} -{V00} => {V01}
Generating: N002 (  1,  1) [000001] -----+-----                    t1 =    LCL_VAR   int    V01 arg1         u:1 (last use) $81
IN0002:             i32.load 1 0
Debug: Closing V01 debug range.
                                                        Live vars after [000001]: {V01} -{V01} => {}
                                                                        /--*  t0     int
                                                                        +--*  t1     int
Generating: N003 (  3,  3) [000002] -----+-----                    t2 = *  ADD       int    $100
IN0003:             i32.add
                                                                        /--*  t2     int
Generating: N004 (  4,  4) [000003] -----+-----                         *  RETURN    int    $VN.Void

[AndyAyersMS]

FYI @kg -- start of some emitter work for WASM.

cc @dotnet/jit-contrib

[SingleAccretion]

@dotnet/jit-contrib

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