JIT: boost inlining when callee unboxes an arg

[AndyAyersMS]

Especially so if the caller is passing an exact type. This may lead to the JIT being able to stack allocate the box and promote the underlying payload.

Fixes #104479

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[AndyAyersMS]

@MihuBot

[AndyAyersMS]

On the example from #104479:

; Method Program:<<Main>$>g__BoxTest|0_0():int (FullOpts)
G_M15828_IG01:  ;; offset=0x0000
       sub      rsp, 40
						;; size=4 bbWeight=1 PerfScore 0.25

G_M15828_IG02:  ;; offset=0x0004
       mov      ecx, 42
       call     [System.Number:Int32ToDecStr(int):System.String]
       mov      rdx, rax
       mov      rcx, 0x7FFC28EF66C0      ; Program:<<Main>$>g__Consume|0_2[System.String](System.String)
       call     [Program:<<Main>$>g__Consume|0_2[System.__Canon](System.__Canon)]
       mov      eax, 42
						;; size=35 bbWeight=1 PerfScore 7.00

G_M15828_IG03:  ;; offset=0x0027
       add      rsp, 40
       ret      
						;; size=5 bbWeight=1 PerfScore 1.25
; Total bytes of code: 4

SPMI sees some diffs and quite a few missed contexts.

MihuBot did not see many diffs, however:

15 total methods with Code Size differences (0 improved, 15 regressed), 232918 unchanged.

So we may need a bespoke SPMI to really evaluate the imapact here.