Add v7 to v8 e2e upgrade test

[damiannolan]

We should add an upgrade handler and e2e chain upgrade test for v7 -> v8 which performs the automatic migrations and does some parameter lookups and assertions to make sure everything is set correctly. The test should:

• Check that params migrations worked as expected.
• Check that migration to add metadata to IBC tokens worked as expected.

These two could be done in two separate PRs, but the second check depends on having the overall test set up in the first one.