Refactor send_tx-related methods into plain functions

[soareschen]

Summary

The method CosmosSdkChain::send_tx() method is tightly coupled with the CosmosSdkChain struct, with deeply nested method calls. This makes it challenging to use the functionality without spawning the entire relayer. This is because the construction of CosmosSdkChain is not straightforward, and involves a lot of indirection through other structures such as ChainHandle and ChainRuntime.

This complication is the main reason why ibc-test-framework currently performs token transfer by calling the gaiad command, because the current design of send_tx() does not allow such simple functionality without a ChainHandle. However since ChainHandle is configured with a global wallet that cannot be changed, this presents challenges of reusing the same ChainHandle to perform transfer for different wallets.

Moving forward, if we want to improve the relayer performance by parallelizing the query operations and send_tx operations, it is also necessary to do this refactoring so that they do not end up in the same struct CosmosSdkChain.

---

For Admin Use

• Not duplicate issue
• Appropriate labels applied
• Appropriate milestone (priority) applied
• Appropriate contributors tagged
• Contributor assigned/self-assigned