Implement conversion from IceResult into BreadcrumbTreeNode.

I believe this change will remove an extra heap allocation I was doing in the new_breadcrumbs_* functions for the explicit context by adding support for converting from Rc<dyn ContextElement> to Rc<dyn IntoContextElement> without copying the underlying data. This should allow conversion of the IceResult::Owned variant to the BreadcrumbTreeElement::Owned variant without extra copying.

src/renderer/breadcrumb_tree.rs

@@ -1,5 +1,7 @@
+use crate::renderer::context_element::ContextElement;
 use crate::renderer::context_element::IceResult;
 use crate::renderer::context_element::IntoContextElement;
+use crate::renderer::context_element::IntoRcIce;
 use std::borrow::Borrow;
 use std::rc::Rc;
 
@@ -29,6 +31,15 @@ impl<'a> From<&'a IceResult<'a>> for BreadcrumbTreeElement<'a> {
     }
 }
 
+impl<'a> From<IceResult<'a>> for BreadcrumbTreeElement<'a> {
+    fn from(inp: IceResult<'a>) -> Self {
+        match inp {
+            IceResult::Owned(rc_ce) => BreadcrumbTreeElement::Owned(rc_ce.into_rc_ice()),
+            IceResult::Borrowed(ce) => BreadcrumbTreeElement::Borrowed(ce.from_context_element()),
+        }
+    }
+}
+
 impl<'a> BreadcrumbTree<'a> {
     pub fn new(parent: Option<&'a BreadcrumbTree>, element: BreadcrumbTreeElement<'a>) -> Self {
         BreadcrumbTree {