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/input/settings/optimizer/details.rs

@@ -0,0 +1,59 @@
+//! The `solc --standard-json` input settings optimizer details.
+
+use serde::Deserialize;
+use serde::Serialize;
+
+/// The `solc --standard-json` input settings optimizer details.
+#[derive(Debug, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct Details {
+    /// Whether the pass is enabled.
+    pub peephole: bool,
+    /// Whether the pass is enabled.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub inliner: Option<bool>,
+    /// Whether the pass is enabled.
+    pub jumpdest_remover: bool,
+    /// Whether the pass is enabled.
+    pub order_literals: bool,
+    /// Whether the pass is enabled.
+    pub deduplicate: bool,
+    /// Whether the pass is enabled.
+    pub cse: bool,
+    /// Whether the pass is enabled.
+    pub constant_optimizer: bool,
+}
+
+impl Details {
+    /// A shortcut constructor.
+    pub fn new(
+        peephole: bool,
+        inliner: Option<bool>,
+        jumpdest_remover: bool,
+        order_literals: bool,
+        deduplicate: bool,
+        cse: bool,
+        constant_optimizer: bool,
+    ) -> Self {
+        Self {
+            peephole,
+            inliner,
+            jumpdest_remover,
+            order_literals,
+            deduplicate,
+            cse,
+            constant_optimizer,
+        }
+    }
+
+    /// Creates a set of disabled optimizations.
+    pub fn disabled(version: &semver::Version) -> Self {
+        let inliner = if version >= &semver::Version::new(0, 8, 5) {
+            Some(false)
+        } else {
+            None
+        };
+
+        Self::new(false, inliner, false, false, false, false, false)
+    }
+}