Update names of modules for `tbtc-mg`, `tbtc-v2.ts` and `cross-chain/arbitrum`

[michalinacienciala]

The first three chunks of the module name in ./config/config.json need to represent the repository name. So we have to start with github.com/keep-network/tbtc-v2 when naming module for cross chain arbitrum module. I propose either github.com/keep-network/tbtc-v2/arbitrum or github.com/keep-network/tbtc-v2/cross-chain-arbitrum.

In the same PR we could change the name of github.com/keep-network/tbtc-mg module to github.com/keep-network/optimistic-minting and github.com/keep-network/tbtc-v2.ts to github.com/keep-network/tbtc-v2/typescript (as they're incorrectly named as well).