cmd/compile: constant overflows when assigned to package level var (Go 1.20 regression) [1.20 backport]

[gopherbot]

@tklauser requested issue #58293 to be considered for backport to the next 1.20 minor release.

@gopherbot please consider this for backport to 1.20, it's a regression.

[gopherbot]

Change https://go.dev/cl/466676 mentions this issue: [release-branch.go1.20] cmd/compile: remove constant arithmetic overflows during typecheck

[gopherbot]

Closed by merging 7302f83 to release-branch.go1.20.