Add options to control the new Builtin Box Drawing Glyphs

### Description of the new feature

Since the new Builtin Box Drawing Glyph feature is parametric, exposing some of it to the user could be beneficial.

Specifically Line Width and Roundiness is most useful if a user wants to emulate the look of the original box drawing characters.

### Proposed technical implementation details

_No response_

Start by locating the Builtin Box Drawing Glyph implementation and the existing user-option or configuration handling. Determine how Line Width and Roundiness are exposed and verify that changing those options alters the glyph rendering as intended.

Written by the indexing model from the issue text.