* ui: Delete a bunch of CSS that we recently moved elsewhere
* ui: Add some masking placeholders
* Switch out hashicorp logo for one from structure-icons
* Change copy-button to use new copy-action icon
* Change secret-button to use new visibility-hide/show icons
* New folder icon for KVs
* Cleanup some of the icons we no longer use
* Switch from %with-exit to standard-like %with-exit-icon
* Move all chevrons to use structure-icons properly
* Use star-fill as much as possible
* Remove the remaining icons from icons/index plus the file itself
1. Amends our `base` animation placeholder to always reset
transition-duration. This has no effect on other components that are
already using this animation.
2. Adds a confirming class whenever a key is pressed, to show the green
tick. Uses CSS via `transition-delay` for debouncing.