Add option to run ddb with observatory
Add option to run ddb with observatory

- Add arg parsing for both `--observe` and `--vm-service-port` for the
  cases where we need to specify a port other than the default. We need
  both since we can't treat the same name as either a flag or an option
  based on whether a value was given, which is the behavior of the VM.
- Follow the `debug` paths when any of `--debug`, `--observe`, or
  `--vm-service-port` is used.
- Whenever using observatory always use `--pause-isolates-on-start`
  since the process would otherwise finish before getting a chance to
  use it.

Change-Id: I30c3f9136ba9a7e8bea4220f88026b13963efc21
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/117595
Auto-Submit: Nate Bosch <dc212c74d8afde9c690fdd09e74d3e5c5d5a3de0@google.com>
Reviewed-by: Nicholas Shahan <03847abd2d8aadfe859ecb98095a31f9f515dc47@google.com>

dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk