[ruby/prism] Split Prism::Loader#load_node in one lambda per node type

* Otherwise load_node is too big to compile and is forced to run in interpreter:
  https://github.com/oracle/truffleruby/issues/3293#issuecomment-1759730996
* For the benchmark at https://github.com/oracle/truffleruby/issues/3293#issuecomment-1759790280
  TruffleRuby Native 23.1.0:
  Before: 10.574041 After: 5.592436
  JRuby 9.4.3.0:
  Before: 7.037780 After: 3.995317
  JRuby 9.4.3.0 -Xcompile.invokedynamic=true:
  Before: 7.047832 After: 2.269294

a592ec346a

prism/templates/lib/prism/serialize.rb.erb

@@ -47,6 +47,7 @@ module Prism
         @constant_pool = nil
 
         @source = source
+        define_load_node_lambdas unless RUBY_ENGINE == 'ruby'
       end
 
       def load_encoding
@@ -194,6 +195,7 @@ module Prism
         load_constant(index - 1) if index != 0
       end
 
+      if RUBY_ENGINE == 'ruby'
         def load_node
           type = io.getbyte
           location = load_location
@@ -222,6 +224,41 @@ module Prism
             <%- end -%>
           end
         end
+      else
+        def load_node
+          type = io.getbyte
+          @load_node_lambdas[type].call
+        end
+
+        def define_load_node_lambdas
+          @load_node_lambdas = [
+            nil,
+            <%- nodes.each do |node| -%>
+            -> {
+              location = load_location
+              <%- if node.needs_serialized_length? -%>
+              load_serialized_length
+              <%- end -%>
+              <%= node.name %>.new(<%= (node.fields.map { |field|
+                case field
+                when Prism::NodeField then "load_node"
+                when Prism::OptionalNodeField then "load_optional_node"
+                when Prism::StringField then "load_string"
+                when Prism::NodeListField then "Array.new(load_varint) { load_node }"
+                when Prism::ConstantField then "load_required_constant"
+                when Prism::OptionalConstantField then "load_optional_constant"
+                when Prism::ConstantListField then "Array.new(load_varint) { load_required_constant }"
+                when Prism::LocationField then "load_location"
+                when Prism::OptionalLocationField then "load_optional_location"
+                when Prism::UInt32Field, Prism::FlagsField then "load_varint"
+                else raise
+                end
+              } + ["location"]).join(", ") -%>)
+            },
+            <%- end -%>
+          ]
+        end
+      end
     end
 
     TOKEN_TYPES = [