Simplify and optimize Prism::Node#tunnel

* By comparing byte offsets which folds 3 branches into 1.
* Also avoids allocation of Location objects.

Author: eregon

templates/lib/prism/node.rb.erb

@@ -184,24 +184,14 @@ module Prism
       queue = [self] #: Array[Prism::node]
       result = [] #: Array[Prism::node]
 
+      line_offset = source.offsets[line - 1] #: Integer
+      search_offset = line_offset + column
+
       while (node = queue.shift)
         result << node
 
         node.compact_child_nodes.each do |child_node|
-          child_location = child_node.location
-
-          start_line = child_location.start_line
-          end_line = child_location.end_line
-
-          if start_line == end_line
-            if line == start_line && column >= child_location.start_column && column < child_location.end_column
-              queue << child_node
-              break
-            end
-          elsif (line == start_line && column >= child_location.start_column) || (line == end_line && column < child_location.end_column)
-            queue << child_node
-            break
-          elsif line > start_line && line < end_line
+          if child_node.start_offset <= search_offset && search_offset < child_node.end_offset
             queue << child_node
             break
           end