[Chronik] Protobuf & HTTP error response handling

Summary:
Add two structs:

1. Protobuf, an extractor and response type for specific protobuf messages.
2. ReportError, a newtype around Report, which can be turned into an HTTP response.

Also add chronik.proto (currently containing only Error) + prost protobuf building using build.rs.

Depends on D13203.

Test Plan: cargo test

Reviewers: Fabien, #bitcoin_abc

Reviewed By: Fabien, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D13204