Introduce project settings for enabling prebuilds for branches, pull requests, etc.

Problem to solve

Following the problem statement in https://github.com/gitpod-io/gitpod/issues/7425, 🅰️ prebuilds are only enable for Github repositories for the default branch and 🅱️ prebuilds are not enabled when adding a repository as project.

For GitHub repositories, when installing the GitHub App, prebuilds are enabled by default for the default branch. For enabling prebuilds for all branches, a user will need to defien this in .gitpod.yml, see relevant docs.

For GitLab and Bitbucket repositories, when adding aproject a webhook is installed. However, enabled are not enabled, see #7424 and pending PR in #7422. Prebuilds are also not enabled when adding a project, following the pattern used for GitHub repositories.

This makes enabling prebuilds for all branches a less discoverable option and more difficult to set up.

Proposal

Introduce a preference in project settings that allows enabling or disabling prebuilds for a) branches, b) pull requests, c) pull requests from forks, as well as, enabling or disabling e) add check, f) add comment, and g) add badge.

Start by reading the problem statement in #7425 and the related references #7424 and #7422 to understand the existing prebuild behavior for GitHub, GitLab, and Bitbucket projects. Done means project settings provide controls for branch, pull request, and fork prebuilds, plus checks, comments, and badges, with enabling and disabling reflected consistently.