Add support for using diesel async for migrations to avoid pq-sys dep

[banool]

Summary

The CLI uses the processor lib for the local testnet. This means, so long as we want the local testnet to support this feature, we cannot depend on pq-sys, since that would require that all CLI users have postgres dynamic libraries on their system, which we cannot assume (nor enforce, since we don't use package managers in all cases).

To address this, we add a new feature called libpq in which we enable the postgres feature of the diesel crate. Since the CLI is an edge case, we enable this feature by default. In the code we then have two implementations of run_migrations based on whether the feature is enabled or not.

Here is the relevant change on the CLI side: aptos-labs/aptos-core#12568.

Test Plan

CI for now, including the new check against banned deps.

I tested that this works from the local testnet and it does!