Consider adding form elements to the theme.json elements block #34198
Description
What problem does this address?
A theme will want to have a specific design for its form elements that is consistent across blocks (be them core blocks or third-party). Ideally, if the user wants to alter this design, their changes should expand through all affected blocks from Global Styles, not just one by one (if I want my buttons to be red, I want ALL buttons on the site to be red, not just the button block).
Right now some of the blocks that have form elements don't let you style them or they do so very limitedly. Examples of these are the Search Block, the File Block and the Post comments form Block. The only way for a theme to make them consistent with each other is via CSS.
What is your proposed solution?
We could have buttons, inputs, textareas, labels, selects... be styled within styles.elements on theme.json and have the blocks using them use these styles as presets and in the future surface this in the Global Styles sidebar for the user to change too.