[UX] Project Browser: Add links with helper actions (configure/settings/enable) next to project installation status.

If a project is already downloaded and installed, there is a "already enabled" indicator in the place of the "add to installation queue" link:

How about we turned this to a link to the project config page (if the project has one)?

• for already installed layouts, this link could be static, pointing to /admin/structure/layouts/settings.
• for already installed themes, we should be linking to /appearance/settings/%theme_name% (if the theme has settings).
• for already installed modules, we should be linking to whatever is in the configure = entry in their .info files.

If the theme/module/layout is downloaded but not enabled, then show an 'enable' link that points to the respective project type manage page.

~~PR by @klonos: https://github.com/backdrop/backdrop/pull/1647~~ PR by @klonos: https://github.com/backdrop/backdrop/pull/2797