Closes#8823https://github.com/enso-org/enso/assets/6566674/966576ec-6507-401c-98d3-bd71c2ffc6b2
Adds a basic text widget for text literals.
### Important Notes
Several known restrictions:
- Separators would always be replaced with single quotation marks. All types of separators in Enso are supported though, and they would be correctly escaped if needed.
- Logic for widget selection probably needs refinement (works for text literals and `Text` types, but does not work for `Text | Integer`, for example)
- **(!)** There is a very annoying issue when the input field suddenly loses focus, closing the editing mode and discarding any changes. Debugging shows that it happens when we receive an engine update (and probably recreate the node component/widget tree (???)). It requires a separate investigation.
Part of #8518Closes#8822
The drop downs were missing, because WidgetFunction had a higher score than them and took precedence. The fix was to adjust scores, so drop down is before both argument name and function. Generally, any widget expecting to "overlap" existing code (and possibly further widgets) should go before WidgetFunction.
# Important Notes
* Extended mockExpressionUpdate to accept a subexpression of a node. Also, I removed it from GraphDb - I want this function to have as little impact on app code as possible.
