Improve performance of connection info in the script editor

[Paulb23]

Hopefully resolved most of the performance issues with the connection info in the script editor.

The majority of the time was spent in get_language()->find_function as it parses the script line by line for the function. Changing this to has_method / get_member_line improves performance as it uses the preparsed script, however, it will now require a valid script for it to work.

It now keeps a Set of methods that already have a connection, saving having to search for it again.

Lastly, swapped checking for a valid texture resource and string for a plain bool.

should close #32236

[akien-mga]

Thanks!