Improve prebuild-in-progress page layout and actions as well as make workspace start sequence clearer

Problem to solve

Following up from https://github.com/gitpod-io/gitpod/pull/9904#discussion_r871268558, the prebuild-in-progress phase:

1. Happens before the workspace loading phases (Checking, Creating, & Starting), however, it's not clear if it takes place before or after the rest of the workspace start phases.
2. Does not re-use the prebuild log output component from the prebuild page, see https://github.com/gitpod-io/gitpod/issues/9132.
3. Currently hijacks the title element from the existing loading phases of the workspace start page to indicate it's about the prebuild-in-progress phase.
4. Does not feel connected with the rest of the workspace start phases.

Proposal

Since the existing loading phases of the workspace start page aim to abstract the sub-states of the loading cycle to make the loading friendlier to the user, we could consider 🅰️ reusing the same element from the prebuilds pages (see https://github.com/gitpod-io/gitpod/issues/9132) where we could surface these sub-states of the prebuild phase and 🅱️ provide better visibility of the step sequence.

BEFORE	AFTER

In short, to break things down into smaller minimum viable changes (MVC) if needed:

1. Introduce a Preparing loading phase for the prebuild-in-progress phase
2. Additionally, consider re-using the prebuild log output element for better associating prebuilds across the product as well as surface potential sub-states of the prebuild-in-progress phase as well as improve the UX of the actions available to users, see https://github.com/gitpod-io/gitpod/issues/9132.

Start with the prebuild-in-progress page and the existing workspace start loading phases described in the issue, then review the linked pull request discussion and issue 9132. Done means the preparing phase and workspace start sequence are clearer, with the proposed prebuild log output and improved user actions considered or implemented.