feat: Add ability to inspect build information and features at runtime

Also re-adds ability to inspect used features

src/core/info/introspection.rs

@@ -0,0 +1,7 @@
+//! Information about features the crates were compiled with.
+//! Only available for crates that have called the `introspect_crate` macro
+
+use std::collections::BTreeMap;
+
+pub static ENABLED_FEATURES: std::sync::Mutex<BTreeMap<&str, &[&str]>> =
+	std::sync::Mutex::new(BTreeMap::new());

src/core/info/mod.rs

@@ -1,3 +1,4 @@
+pub mod introspection;
 pub mod room_version;
 pub mod version;