[Chronik] Require at least Protobuf 3.0.0 for Chronik functional tests

Summary: Chronik uses the proto3 syntax, which isn't supported in older protobuf compilers. proto3 was introduced in 3.0.0, so this is the minimal possible version.

Test Plan: cmake .. -GNinja -DBUILD_BITCOIN_CHRONIK=on

Reviewers: Fabien, #bitcoin_abc

Reviewed By: Fabien, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D13330