[META] Views Contextual Filtering Improvements

There are a few tickets with the aim of allowing contextual changes to the views module view used within the entity browser. Each has merit and each is altering the view slightly differently. The aim of this issue is to see if there is any coordination between the issues that can be achieved and to make sure there isn't needless redundancy.
To do:

• #3041639: Add parent entity to #widget_context
• #2790951: Provide for contextual filter argument option on field widget - Adds option on field widget for arguments passed to the view using tokens
• #3038854: Provide hook to alter view executable before render in view widget - Provides an alter hook before the view is rendered with contextual information available. This could be used to set the arguments on the view, for example if you wanted to configure a view with current node id as a contextual filter, this is one way how you could add the view argument.
• #3032401: Provide docs on how to extend Entity Browser Display Plugins - Ticket asking for documentation
• #2832240: Configure path arguments for View widget via UI - Adds option on the view widget plugin to specify url segments.
• #2957134: Add tokens for embedded page path; allow them to be used in widget settings
• #3040938: Pass current selection in field_widget to #widget_context

Fixed

• #3039038: Provide views filter that limits based based on allowed bundles - Provides a ContextualBundle view filter plugin that updates bundles in Entity Browser based on #widget_context. Borrows #widget_context code from 2865928.
• #2865928: Provide method for views widget to filter based on context - Provides a views default argument plugin (EntityBrowserWidgetContext) that works with #widget_context. Passed bundles to view in field_widget, entity_embed and inline_entity_form_context. This is awesome and should get merged as soon as possible.