Use action button for a consistent loading button behaviour with vanilla guidelines

[edlerd]

Done

• replace all occurrences of submit button with action button, to have a consistent loading button behaviour with vanilla guidelines
• remove submit button component

QA

1. Run the LXD-UI:
   • On the demo server via the link posted by @webteam-app below. This is only available for PRs created by collaborators of the repo. Ask @mas-who or @edlerd for access.
   • With a local copy of this branch, run as described here.
2. Perform the following QA steps:
   • check occurrences of the submit button for visual regressions

[webteam-app]

Demo starting at https://lxd-ui-663.demos.haus

[mas-who]

code looks good, spot QA'd a few places where SubmitButton was replaced and it also looks good 👍 let's wait for @piperdeck for the design review