go/types: add tests for conversion of non-constant untyped values
go/types: add tests for conversion of non-constant untyped values

This was fixed by CL 242084. Retroactively add some tests that would
have failed before the fix.

Also, remove some existing duplicate tests.

Change-Id: I95f7a215d4a9651ded6d739f89c574f33f573c60
Reviewed-on: https://go-review.googlesource.com/c/go/+/251397
Run-TryBot: Robert Findley <9179eee875d1ee628c37fb47d7e749e855ffd21f@google.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Robert Griesemer <a6752097faebf1f02d80107d77a9be009089afe3@golang.org>

nawawi/go,CAFxX/go,nawawi/go,CAFxX/go,golang/go,golang/go,golang/go,CAFxX/go,cloudflare/go,cloudflare/go,CAFxX/go,cloudflare/go,golang/go,golang/go,nawawi/go,golang/go,nawawi/go,cloudflare/go,cloudflare/go,CAFxX/go,golang/go,cloudflare/go,golang/go,nawawi/go,CAFxX/go,CAFxX/go,cloudflare/go,CAFxX/go,nawawi/go,nawawi/go,cloudflare/go,nawawi/go