icons: re-visiting exisiting icon-set styling

hello,

This stems from my minor nit, that the icons provided via vanilla-framework when put alongside the Ubuntu font look comparatively thick (im assuming the icon stroke length is more than 1px). As, such I had couple of thoughts that I wanted to bring to improve the look of the exisiting icon-set:

- Consider aligning the Icon design to Yaru's scalable stroke length of 1px.
- Modernize and perhaps sync the icon representation with its counterpart already present in Yaru.
- Inclusion of new-icons that can be utilized for common action metaphors (from top of my head ex: paste-icon, clear-all icon, dark-mode icon)

_Note: this issue was created from pr: #5500_

Start by reviewing PR #5500 and the existing icon set in vanilla-framework, then compare the icons with the Ubuntu font and Yaru counterparts mentioned in the issue. Clarify which styling, synchronization, and new-icon proposals are in scope; done should be a decided, consistent icon-set update with agreement on the requested additions.

Written by the indexing model from the issue text.