"Content item" widget gives validation error if attempting to use a piece of content with a title longer than 128 characters

Problem/Motivation

If you try to add a "Content Item" widget with a "Piece of content" referring to a node with a title longer than 128 characters, you'll get the following validation errors:

exposed cannot be longer than 128 characters but is currently 161 characters long.

title cannot be longer than 128 characters but is currently 161 characters long.

Steps to reproduce

1. Add a Content Item widget
2. Try to load a node content item with a longer title (longer than 128 characters)
3. Notice that you can't save the widget due to the error

Proposed resolution

There's an upstream patch that seems to have the right idea: #1973580: Term reference filter autocomplete ('is one of', 'is none of') has a maximum length of 128 characters

However, it doesn't seem super likely that it'll be merged (that issue is already 8 years old, and the patch is 2 years old). We can use a form alter to fix it in panopoly_widgets.

Remaining tasks

1. Write patch
2. Review
3. Merge!

User interface changes

None.

API changes

None.

Data model changes

None.