Add automated test for pg_upgrade

[adamguo0]

Describe the problem

We should make sure new changes to pg_tle do not break when they go through pg_upgrade.

Describe the proposal

We can potentially do this with a TAP test, but our tests are currently set up to run on a single version of Postgres. Will need to do more investigating

[jnasbyupgrade]

FYI you can find an example of how to do this at https://github.com/theory/pgtap/blob/main/test/test_MVU.sh