feat: implement x/callback module

[spoo-bar]

Closes: #479

RFC: https://github.com/orgs/archway-network/discussions/25 AIP: https://github.com/archway-network/archway/issues/477

The implementation spec can be found under x/callback/spec

[codecov[bot]]

Codecov Report

Attention: 258 lines in your changes are missing coverage. Please review.

Comparison is base (8c8b7e0) 65.90% compared to head (d6ffa88) 65.61%.

Files	Patch %	Lines
x/callback/types/msg.go	0.00%	55 Missing :warning:
x/callback/types/events.go	0.00%	39 Missing :warning:
x/callback/keeper/msg_server.go	72.07%	28 Missing and 3 partials :warning:
x/callback/types/callback.go	30.55%	21 Missing and 4 partials :warning:
x/callback/keeper/callback.go	80.85%	12 Missing and 6 partials :warning:
x/callback/keeper/grpc_query.go	68.00%	15 Missing and 1 partial :warning:
x/callback/module.go	65.21%	16 Missing :warning:
x/callback/keeper/fees.go	64.70%	8 Missing and 4 partials :warning:
x/callback/types/genesis.go	42.85%	12 Missing :warning:
x/callback/keeper/keeper.go	79.16%	7 Missing and 3 partials :warning:
... and 4 more

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #501 +/- ## ========================================== - Coverage 65.90% 65.61% -0.30% ========================================== Files 64 80 +16 Lines 3916 4633 +717 ========================================== + Hits 2581 3040 +459 - Misses 1207 1436 +229 - Partials 128 157 +29 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.