Initial fix for double caret inserting in NodePath

Additional cases where prepending doubles up

Moved code to helper function

Added unit tests

Lookup caret character instead of passing position

Switched to using the parsed type

Adding safety checks and various cleanup

modules/gdscript/tests/scripts/completion/argument_options/string_literals/add_node_path_tween_prepended.cfg

@@ -0,0 +1,11 @@
+[input]
+add_node_path_literals=true
+[output]
+include=[
+    {"insert_text": "\"property_of_a\""},
+    {"insert_text": "\"name\""},
+]
+exclude=[
+    {"insert_text": "^\"property_of_a\""},
+    {"insert_text": "^\"name\""},
+]

modules/gdscript/tests/scripts/completion/argument_options/string_literals/add_node_path_tween_prepended.gd

@@ -0,0 +1,8 @@
+extends Node
+
+const A = preload("res://completion/class_a.notest.gd")
+
+func _ready() -> void:
+    var a := A.new()
+    var tween := get_tree().create_tween()
+    tween.tween_property(a, ^"➡")

modules/gdscript/tests/scripts/completion/argument_options/string_literals/add_string_name_input_event_prepended.cfg

@@ -0,0 +1,9 @@
+[input]
+add_string_name_literals=true
+[output]
+include=[
+    {"insert_text": "\"test_input_action\""},
+]
+exclude=[
+    {"insert_text": "&\"test_input_action\""},
+]

modules/gdscript/tests/scripts/completion/argument_options/string_literals/add_string_name_input_event_prepended.gd

@@ -0,0 +1,3 @@
+func _input(event: InputEvent) -> void:
+    event.is_action_pressed(&"➡")
+    pass