Implement UserDataHolder for EditorDataContext

[PHPirates]

This PR fixes Hannah-Sten/TeXiFy-IDEA#2230

How to reproduce the issue

• In build.gradle.kts, add a dependency on plugin TeXiFy-IDEA: nl.rubensten.texifyidea:0.7.14
• runIde
• Go to Settings > Editor > Code Style, set Hard wrap at to 120 characters and enable Wrap on typing.
• Create a LaTeX file (.tex) and paste the following content:

\begin{itemize}
    \item This is the first item: pressing enter at the end of this line will insert an \verb|\item| on the next line.
    \item This line should hard-wrap to a next line without inserting an \verb|\item| in front of it, when typing here:
\end{itemize}

• Continue typing after ... when typing here:
• Expected behaviour, and this is what happens when IdeaVim is not installed: the text is wrapped to the next line, no \item is inserted.
• Actual behaviour with IdeaVim installed: \item is inserted at the beginning of the next line.

Issue description

• The AutoHardWrapHandler:188 saves data for a custom key to the data context. Without IdeaVim, the data context is an EdtDataContext, with IdeaVim the EditorDataContext which has as contextDelegate the EdtDataContext.
• TeXiFy implements a typed handler, which checks for this data key in order to determine whether an auto hard wrap is in progress.
• Without IdeaVim, TeXiFy can retrieve the data from the context. With IdeaVim, the data cannot be retrieved from the context (DataManager#loadFromDataContext) because the context is not a UserDataHolder.

Issue fix

This PR fixes that last point, so that the IdeaVim data context now correctly delegates the user data.
I verified that it fixes the problem, but please check if this doesn't break something else.

[AlexPl292]

Hi there! Thank you for your contribution.
That seems to be a save fix, so I'll merge this without additional checks.

[PHPirates]

Great, thanks a lot!