[UX] Layout path selection: Make it more user friendly

From a Gitter conversation but similar sentiments at #2411 and #2306

Sam Stamport @ColumbiaBlooms 07:51 Please explain the relationship between Path and Visibility Conditions on the layout configuration page in the UI.

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docwilmot @docwilmot Apr 04 14:15 @Gormartsen idea: On the Add layout page, offer the user two options (radio list): create a layout for existing entities (will need to work on the terminology) OR your own path Selecting the first option would reveal a select list of entity types. Maybe clicking one could immediately reveal an option to pick a bundle type. Selecting the second option reveals a textfield to type a path into This wouldn't avoid confusion for complicated paths like other-entity/%/subpath/% but would at least simplify the majority of common use cases. Thoughts?

docwilmot @docwilmot 13:16 Add layout page Entering custom path Selecting an entity to override its paths.

Gregory Netsas @klonos 17:33 @docwilmot I personally like the idea of making the process of creating layouts be wizard-based. I wonder if adding an additional step (and thus increasing the time/clicks required to create a layout) will disappoint advanced users. On the other hand, we could add this as a "layout path wizard" next to the path field. Advanced users would still be able to enter the path as they used to, but there will be a "Help me with this" button that pops-up a dialog next to it for users that do not understand how this works.