Fixed an exception when destroying an entry and updating the text variable

[Nerogar]

This fixes an exception that occurs after destroying a CtkEntry with a text variable and then updating that text variable.

trace_add is called when the entry is created, but trace_remove was never called.

The exception was
_tkinter.TclError: invalid command name

[FedericoSpada]

Hi,
it is also missing the proper management when the textvariable is replaced using the configure() method. Can you add it by copying what has been done for the other widgets?

While you are at it, can you replace the "textvariable" name for CTkEntry with just "variable"?
"textvariable" has been used in other widgets to dynamically change the fixed text that describes the content of the widget, not the actual value that the user can change. For this value, the other widgets always use the "variable" parameter.
Thanks