fix!: Don't add padding around zero-width fields.

[gonfunko]

The basics

• I validated my changes

The details

Resolves

Fixes#8699

Proposed Changes

This PR makes several changes around zero-width fields:

• Fields no longer prevent themselves from having zero-width by swapping their (empty) display text with a non-breaking space character
• [BREAKING] The long-deprecated support for re-rendering a field by setting its width to 0 has been removed
• [BREAKING] The Field.NBSP static constant has been removed
• The built-in renderers have been updated to not insert padding after zero-width fields to avoid doubled-up padding around invisible fields

[cpcallen]

• Fields no longer prevent themselves from having zero-width by swapping their (empty) display text with a non-breaking space character

@gonfunko: How should fields prevent themselves from having zero width? (Relevant because some of the plugins are still using .NBSP.)