[BridgeCli]: separate required configuration based on the command

[kisialiou]

In the current CLI implementation, the user must provide all the configurations either through config file or command line arguments even if they are not required.

Example: running bridge-cli testnet omni-connector near-log-metadata requires solana_keypair being specified. This makes no sense and complicates the usage.

Proposal: for each command specify required clients and initialize only them before the execution.