Remove deprecated Project DB config feature

[jankeromnes]

Description

The Project DB config is now deprecated and unused. This PR removes it.

• The "Project Configurator" feature was first introduced as part of the New Project flow
• Then it was removed from the New Project flow, and kept as an extra feature in the Project Settings menu
• Then it was superseded by auto-generated .gitpod.ymls in every workspace: Always Infer .gitpod.yml #6921
• Additionally, we automatically reject webhooks when there is no explicit .gitpod.yml file in the repo, so Project DB configs were actually never used for regular prebuilds:

  gitpod/components/server/ee/src/prebuilds/prebuild-manager.ts

  Lines 301 to 305 in 384a0e7

  	shouldPrebuild(config: WorkspaceConfig | undefined): boolean {
  	if (!config || !config._origin || config._origin !== "repo") {
  	// we demand an explicit gitpod config
  	return false;
  	}

Related Issue(s)

Fixes #9102

How to test

1. Adding new Projects should still work
2. Prebuilds should still work
3. The "Configuration" feature/tab should no longer exist in Project Settings

Release Notes

NONE

Documentation

Werft options:

• /werft with-preview

[jankeromnes]

/werft run

👍 started the job as gitpod-build-jx-rm-configure.1
(with .werft/ from main)