Add lazy loader pattern for CLI command execution

Extend `BackstageCommand.execute` to accept either a direct function or a
`{ loader }` object for lazy loading command implementations. Convert
several build and migrate commands to use the new pattern. Switch from
`program.parse` to `program.parseAsync` to properly await async actions.

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

packages/cli/package.json

@@ -81,6 +81,7 @@
     "buffer": "^6.0.3",
     "chalk": "^4.0.0",
     "chokidar": "^3.3.1",
+    "cleye": "^2.2.1",
     "commander": "^14.0.3",
     "cross-fetch": "^4.0.0",
     "cross-spawn": "^7.0.3",