Separate condition plugin for entity reference fields

Problem/Motivation

We faced the following issues with entity reference fields:

• Current UI for conditions on entity reference fields is not too user-friendly. Users have to enter IDs manually.
• Values are saved as numerical IDs, which means such configs can't be deployed in most cases.
• It's not possible to enter multiple values for comparison.

Proposed resolution

The MR introduces a separate condition plugin for entity reference fields with autocomplete input for multiple values. It also saves the IDs as UUID.

Remaining tasks

• Port it to the 2.0.x branch.
• Integrate the changes with the general field value plugin suggested in .
• Update the module documentation.

User interface changes

It adds separate condition type for entity reference fields.

API changes

None.

Data model changes

None.