Refactor naming and crates info (#8)

* Refactor naming and crates info

This commit:
* changes workspace crates to have a `wiggle_` prefix in names
* rename `memory` module of `wiggle-memory` crate to `runtime`
* fixes authors of all crates

* Rename wiggle memory crate to runtime

crates/runtime/src/borrow.rs

@@ -0,0 +1,67 @@
+use std::collections::HashMap;
+
+use crate::region::Region;
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub struct BorrowHandle(usize);
+
+#[derive(Debug)]
+pub struct GuestBorrows {
+    immutable: HashMap<BorrowHandle, Region>,
+    mutable: HashMap<BorrowHandle, Region>,
+    next_handle: BorrowHandle,
+}
+
+impl GuestBorrows {
+    pub fn new() -> Self {
+        GuestBorrows {
+            immutable: HashMap::new(),
+            mutable: HashMap::new(),
+            next_handle: BorrowHandle(0),
+        }
+    }
+
+    fn is_borrowed_immut(&self, r: Region) -> bool {
+        !self.immutable.values().all(|b| !b.overlaps(r))
+    }
+
+    fn is_borrowed_mut(&self, r: Region) -> bool {
+        !self.mutable.values().all(|b| !b.overlaps(r))
+    }
+
+    fn new_handle(&mut self) -> BorrowHandle {
+        let h = self.next_handle;
+        self.next_handle = BorrowHandle(h.0 + 1);
+        h
+    }
+
+    pub fn borrow_immut(&mut self, r: Region) -> Option<BorrowHandle> {
+        if self.is_borrowed_mut(r) {
+            return None;
+        }
+        let h = self.new_handle();
+        self.immutable.insert(h, r);
+        Some(h)
+    }
+
+    pub fn unborrow_immut(&mut self, h: BorrowHandle) {
+        self.immutable
+            .remove(&h)
+            .expect("handle exists in immutable borrows");
+    }
+
+    pub fn borrow_mut(&mut self, r: Region) -> Option<BorrowHandle> {
+        if self.is_borrowed_immut(r) || self.is_borrowed_mut(r) {
+            return None;
+        }
+        let h = self.new_handle();
+        self.mutable.insert(h, r);
+        Some(h)
+    }
+
+    pub fn unborrow_mut(&mut self, h: BorrowHandle) {
+        self.mutable
+            .remove(&h)
+            .expect("handle exists in mutable borrows");
+    }
+}