Improved fee-related error message

[ljoss17]

Closes: #1400

Description

This PR adds a match case for the SDK Err(13), which is triggered when the configured gas price is lower than the minimum gas price allowed on the chain.

Trigger the error

It is possible to trigger the error using gm:

gm.toml

[global]
gaiad_binary="<Path to gaiad binary. E.g: /opt/bin/gaiad>"

[global.hermes]
binary="<Path to hermes binary. E.g: /home/.hermes/bin/hermes>"


[a]
  add_to_hermes = true
  ports_start_at = 27000

[b]
  add_to_hermes = true
  ports_start_at = 27030

1. use the above gm config
2. gm start, gm hermes config, gm hermes keys
3. gm stop a
4. open the configuration file for the chain a, located in .gm/a/config/app.toml
   • set minimum-gas-prices = "0.017stake"
5. gm start a
6. replace the gas configuration for chain a in the .hermes/config.toml
   • set gas_price = { price = 0.001, denom = 'stake' }
7. hermes create client a b
   • now we should see the error with the diagnostic for the error

---

PR author checklist:

• Added changelog entry, using unclog.
• Added tests: integration (for Hermes) or unit/mock tests (for modules).
• Linked to GitHub issue.
• Updated code comments and documentation (e.g., docs/).

Reviewer checklist:

• Reviewed Files changed in the GitHub PR explorer.
• Manually tested (in case integration/unit/mock tests are absent).

[adizere]

Great work Luca!