Lump Harbormaster build steps into groups

Summary:
Ref T8089. We have a lot of broken/confusing/prototype build steps that I want to hide from users when we unprototype Harbormaster.

The dialog is also just kind of unwieldy.

Organize this UI a little better and put all the sketchy junk in a "prototypes" group that you can't see unless prototypes are enabled.

This doesn't break anything (the old steps will still work fine), but should reduce user confusion.

Test Plan:
Old UI:

New UI (prototypes off):

New UI (prototypes on):

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T8089

Differential Revision: https://secure.phabricator.com/D13803