chore: rename gravity module

[byte-bandit]

Related Github tickets

• https://github.com/VolumeFi/paloma/issues/1801

Background

As a Paloma user, I want the "gravity2" module to have a name that better represents it's functionality (it was heavily modified from the original gravity source) and I want the (cli) documentation to make clear that it is multichain instead of just for ETH.

[!CAUTION] This change is breaking and will remove any data stored within the Gravity store.

Testing completed

• [x] test coverage exists or has been added/updated
• [x] tested in a private testnet

Breaking changes

• [x] I have checked my code for breaking changes
• [x] If there are breaking changes, there is a supporting migration.

[taariq]

Wow. That was big and fast! Congrats @byte-bandit