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/solc-json-interface/src/standard_json/output/contract/evm/mod.rs

@@ -0,0 +1,42 @@
+//! The `solc --standard-json` output contract EVM data.
+
+pub mod bytecode;
+
+use std::collections::BTreeMap;
+
+use serde::Deserialize;
+use serde::Serialize;
+
+use self::bytecode::Bytecode;
+use self::bytecode::DeployedBytecode;
+
+/// The `solc --standard-json` output contract EVM data.
+/// It is replaced by PolkaVM data after compiling.
+#[derive(Debug, Serialize, Deserialize, Clone)]
+#[serde(rename_all = "camelCase")]
+pub struct EVM {
+    /// The contract PolkaVM assembly code.
+    #[serde(rename = "assembly", skip_serializing_if = "Option::is_none")]
+    pub assembly_text: Option<String>,
+    /// The contract bytecode.
+    /// Is reset by that of PolkaVM before yielding the compiled project artifacts.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub bytecode: Option<Bytecode>,
+    /// The deployed bytecode of the contract.
+    /// It is overwritten with the PolkaVM blob before yielding the compiled project artifacts.
+    /// Hence it will be the same as the runtime code but we keep both for compatibility reasons.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub deployed_bytecode: Option<DeployedBytecode>,
+    /// The contract function signatures.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub method_identifiers: Option<BTreeMap<String, String>>,
+}
+
+impl EVM {
+    /// Sets the PolkaVM assembly and bytecode.
+    pub fn modify(&mut self, assembly_text: String, bytecode: String) {
+        self.assembly_text = Some(assembly_text);
+        self.bytecode = Some(Bytecode::new(bytecode.clone()));
+        self.deployed_bytecode = Some(DeployedBytecode::new(bytecode));
+    }
+}