Use canonical method IL in scanner's ImportCall

[MichalStrehovsky]

This is necessary so that the scanner can accurately predict what weird things we're going to need later. We're emulating what getCallInfo will do.

Fixes #5648. Note that the F# hello app is still blocked, this time on complex tail calls (#1683).

[charlesroddie]

@MichalStrehovsky "The F# hello app is still blocked, this time on complex tail calls." Have you confirmed that? I would not have expected simple apps like hello world, or even most real-world F# apps, to be blocked by complex tail calls.

[MichalStrehovsky]

It was blocked, but Jan subsequently made a fix to RyuJIT that unblocked it (dotnet/coreclr#17592, followed by #5712).

I think it means we still can't do complex tailcalls, but fewer tailcalls are considered complex.