proto: Add missing serde derives on Protobuf definitions

[romac]

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

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 23.68421% with 29 lines in your changes are missing coverage. Please review.

Project coverage is 59.3%. Comparing base (99ed0b9) to head (acc17cc). Report is 1 commits behind head on main.

:exclamation: Current head acc17cc differs from pull request most recent head 8d01b40. Consider uploading reports for the commit 8d01b40 to get more accurate results

Files	Patch %	Lines
tendermint/src/private_key.rs	0.0%	10 Missing :warning:
tendermint/src/crypto/ed25519/signing_key.rs	0.0%	6 Missing :warning:
tools/proto-compiler/src/constants.rs	0.0%	6 Missing :warning:
tendermint/src/public_key.rs	42.8%	4 Missing :warning:
tendermint/src/crypto/ed25519/verification_key.rs	0.0%	3 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1389 +/- ## ======================================= - Coverage 60.1% 59.3% -0.8% ======================================= Files 271 271 Lines 26221 26549 +328 ======================================= - Hits 15768 15761 -7 - Misses 10453 10788 +335 ```

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