Fix the ispath SDQL2/Lua wrapper (and add a is_type_in_typecache wrapper) (#90207)

## About The Pull Request

This fixes the `_ispath` SDQL2 / Lua wrapper: it always passed two
arguments, meaning it couldn't be used to just simply check if something
was a path _at all_.

In addition, I just added wrapper around `is_type_in_typecache` (as it's
a define), as that's the whole reason I was using `_ispath` anyways, so
it can't hurt.

## Why It's Good For The Game

things working properly is nice

## Changelog
🆑
fix: The _ispath SDQL2/Lua wrapper can now be used to actually check if
something is a path.
code: Added the _is_type_in_typecache wrapper, for SDQL2 / Lua scripts.
/🆑

---------

Co-authored-by: Ghom <42542238+Ghommie@users.noreply.github.com>

code/modules/admin/verbs/SDQL2/SDQL_2_wrappers.dm

@@ -64,6 +64,8 @@
 	return istype(object, type)
 
 /proc/_ispath(path, type)
+	if(isnull(type))
+		return ispath(path)
 	return ispath(path, type)
 
 /proc/_length(E)
@@ -297,3 +299,6 @@
 	if(!filter_index || filter_index < 1 || filter_index > length(target.filters))
 		return
 	animate(target.filters[filter_index], appearance = set_vars, time, loop, easing, flags)
+
+/proc/_is_type_in_typecache(thing_to_check, typecache)
+	return is_type_in_typecache(thing_to_check, typecache)