Refactor the input handling logic (#48)

* Add support for wrapper types

* Move `FilesWithExtensionIterator` to `core::common`

* Remove unneeded use of two `HashMap`s

* Make metadata structs more typed

* Impl new_from for wrapper types

* Implement the new input handling logic

* Fix edge-case in input handling

* Ignore macro doc comment tests

* Correct comment

* Fix edge-case in deployment order

crates/format/src/case.rs

@@ -1,6 +1,6 @@
 use serde::Deserialize;
 
-use crate::{input::Input, mode::Mode};
+use crate::{define_wrapper_type, input::Input, mode::Mode};
 
 #[derive(Debug, Default, Deserialize, Clone, Eq, PartialEq)]
 pub struct Case {
@@ -10,3 +10,9 @@ pub struct Case {
     pub inputs: Vec<Input>,
     pub group: Option<String>,
 }
+
+define_wrapper_type!(
+    /// A wrapper type for the index of test cases found in metadata file.
+    #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+    CaseIdx(usize);
+);