Script Editor windows are not fully integrated into the Window menu

From Michael Cammer [via the ImageJ mailing list](https://list.nih.gov/cgi-bin/wa.exe?A2=IMAGEJ;7b2fe35d.2007):

In standard ImageJ, each text window is easily accessible from the Window menu. We can select it and then do commands such as:
```javascript
selectWindow("20200725_rawdata.txt");
textdump = getInfo("window.contents");
a = split(textdump);
```
However, in Fiji, the text windows are in the Java text editor, are not listed in the windows menu, and getInfo("window.contents") returns an error that no window can be found.

Therefore, macros we have written for ImageJ with text windows don't work.

Start by reproducing the difference between standard ImageJ and Fiji using the Window menu and the reported macro commands, especially getInfo("window.contents"). Trace how Script Editor text windows are registered and exposed to window commands. Done means those text windows are listed in the Window menu and the macro can select them and read their contents.

Written by the indexing model from the issue text.