cmd/compile: ICE on method value involving imported anonymous interface [1.20 backport]

[gopherbot]

@mdempsky requested issue #58563 to be considered for backport to the next 1.20 minor release.

@gopherbot Please backport to 1.20.

[dmitshur]

@mdempsky Please add a short backport rationale to this backport issue (see https://go.dev/wiki/MinorReleases; "The issue should include a link to the original issue and a short rationale about why the backport might be needed."). Thanks.

[gopherbot]

Change https://go.dev/cl/472620 mentions this issue: [release-branch.go1.20] cmd/compile: relax overly strict assertion

[gopherbot]

Closed by merging 26eeaec to release-branch.go1.20.