Code review feedback.

* Remove `once-cell` dependency.
* Remove function address `BTreeMap` from `CompiledModule` in favor of binary
  searching finished functions directly.
* Use `with_capacity` when populating `CompiledModule` finished functions and
  trampolines.

crates/jit/src/code_memory.rs

@@ -61,6 +61,15 @@ impl<'a> CodeMemoryObjectAllocation<'a> {
     pub fn code_range(self) -> &'a mut [u8] {
         self.buf
     }
+
+    pub fn funcs_len(&self) -> usize {
+        self.funcs.len()
+    }
+
+    pub fn trampolines_len(&self) -> usize {
+        self.trampolines.len()
+    }
+
     pub fn funcs(&'a self) -> impl Iterator<Item = (FuncIndex, &'a mut [VMFunctionBody])> + 'a {
         let buf = self.buf as *const _ as *mut [u8];
         self.funcs.iter().map(move |(i, (start, len))| {
@@ -69,6 +78,7 @@ impl<'a> CodeMemoryObjectAllocation<'a> {
             })
         })
     }
+
     pub fn trampolines(
         &'a self,
     ) -> impl Iterator<Item = (SignatureIndex, &'a mut [VMFunctionBody])> + 'a {