Improve type checker error readability

[tsandall]

In some cases, the type checker errors become overly verbose. E.g,. the following error was generated by trying to union an object and a set:

rego_type_error: or: invalid argument(s)
    have: (set[object<action: set[string], object: string>], object<action: set[string], object: string>, ???)
    want: (set[any], set[any], set[any])

One improvement would be to elide type information so that the top-most differing types are emphasized. For example:

have (set[…], object<…>, ???)
want (set[...], set[...], set[...])

[stale[bot]]

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[stale[bot]]

This issue has been automatically marked as inactive because it has not had any activity in the last 30 days.