fix(tendermint): Fix deserialization from serde_json::Value

[oblique]

Fixes #1474

• Referenced an issue explaining the need for the change
• Updated all relevant documentation in docs
• Updated all code comments where relevant
• Wrote tests
• Added entry in .changelog/

[oblique]

Some questions:

1. CowStr can also be used in any place of tendermint-rs that uses String::deserialize etc. Should I change all of them?
2. Do you like CowStr or should I just use String?

[romac]

Some questions:

1. CowStr can also be used in any place of tendermint-rs that uses String::deserialize etc. Should I change all of them?

This can be done in a follow-up PR :)

2. Do you like CowStr or should I just use String?

CowStr is fine!

[romac]

Can you please add a changelog entry in the appropriate subdirectory in .changelog/? Then I'll gladly merge this :)