feat(next): adds support for edit view description components

[akhrarovsaid]

What?

This PR adds support for distinct edit view descriptions since there was clearly the infrastructure in place for it anyway. This also fixes an issue where collection descriptions were finding their way into document edit views.

Why?

To enable end-users to add their own custom components as descriptions in edit views.

How?

By allowing a new Description custom component in the admin.components.views.edit object.

Before:
Description-before--Payload.webm

After:
Description-after--Payload.webm

Notes:

• I noticed that none of the custom components in renderDocumentSlots are actually getting passed default props. I decided it was likely out of scope for this PR, but can easily add this in. This was fixed.

[DanRibbens]

I see this as a breaking change. In order to get this merged we need to fallback to existing components. In a future major version we can remove the extra collectionConfig?.admin?.components?.Description if we want to. For now somebody will bave to define a Description returning null as a workaround if they wanted to have a list view Description and not edit.Description.

Also, the PR needs documentation changes.