feat: custom load (dsl) implement support

[RickyYCheng]

#1209 highlights a security risk associated with the load/Load DSL function in *.dialogue files.

This PR introduces a Callable field, allowing users to configure the behavior of the load/Load functions. Corresponding tests have been added.

This PR only adds the configuration and does not modify the language server or code hints for *.dialogue files.

For example, this slice of code will be prevent if the load function was set to Callable(). No compile time warnings.

DialogueManager.dialogue_dsl_load = Callable()

$> debug(load("res://icon.svg"))