Fix governor endpoints
A few governor endpoints were handling addresses incorrectly,
which resulted in errors.
* `GET /api/v1/governor/config/{governor_address}`
* `GET /api/v1/governor/status/{governor_address}`
This commit fixes the issue and adds doc comments to prevent the
same caveat from happening again in the future.
### Summary
Context: https://github.com/wormhole-foundation/wormhole-explorer/issues/154
This PR modifies all endpoints that receive an emitter/guardian address to accept a wider range of formats.
After this pull request, all of these are equivalent:
* `0x000000000000000000000000f890982f9310df57d00f659cf4fd87e65aded8d7`
* `000000000000000000000000f890982f9310df57d00f659cf4fd87e65aded8d7`
* `0xf890982f9310df57d00f659cf4fd87e65aded8d7`
* `f890982f9310df57d00f659cf4fd87e65aded8d7`
### Testing plan
* Added unit tests for the parsing code.
* Tested manually a few of the affected endpoints.