gopls/modernize: "for i = range n {}" fix is wrong if there are later uses of i

[adonovan]

@dethi reports:

I found one additional bug in the transformation of i := 0; for i = 0; i < n; i++ -> for i = range n if i is used outside of the for loop body. See the minimal reproduction: https://go.dev/play/p/9tlB2oilyJn

In particular, the postcondition of the original loop is that i has the value n, whereas for the range loop it has the value n-1.

[gopherbot]

Change https://go.dev/cl/652496 mentions this issue: gopls/internal/analysis/modernize: fix bug in rangeint