factor out solc JSON interface crate (#264)

The differential testing framework will make a second consumer. There
seems to be no re-usable Rust crate for this. But we already have
everything here, just needs a small refactor to make it fully re-usable.

- Mostly decouple the solc JSON-input-output interface types from the
`solidity` frontend crate
- Expose the JSON-input-output interface types in a dedicated crate

---------

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

crates/solidity/Cargo.toml

@@ -37,6 +37,7 @@ inkwell = { workspace = true }
 
 revive-common = { workspace = true }
 revive-llvm-context = { workspace = true }
+revive-solc-json-interface = { workspace = true, features = ["resolc"] }
 
 [target.'cfg(target_env = "musl")'.dependencies]
 mimalloc = { version = "*", default-features = false }