Add redirect section to config validation

This MR improves the error messages that are emitted when the redirect section of the configuration are misconfigured.

Error on no disable section in redirect:

configuration error: validation: `storage.redirect` section must include `disable: (bool)`
Usage:
  registry serve <config> [flags]

Flags:
  -h, --help   help for serve

Error on disable given improper type:

configuration error: validation: `storage.redirect.disable` must be a boolean got: "yes" (string)
Usage:
  registry serve <config> [flags]

Flags:
  -h, --help   help for serve