chore(cli): enable backwards compatibility syntax for addons:create

[zwhitfield3]

Description

This PR enables backwards compatible v8.x.x syntax for passing in positional arguments to the heroku addons:create command.

Testing

1. Pull down branch
2. yarn it up
3. Confirm passing positional arguments using old v8.x.x syntax via
   ./bin/run addons:create -a heroku-cli-test-staging heroku-postgresql:private-0 --follow DATABASE
4. Confirm that the addon successfully provisioned a follower database with the positional --follow flag
5. Confirm that the deprecation warning is also visible like so:

 ›   Warning: You’re using a deprecated syntax with the [--follow] flag.
 ›   Add a '--' (end of options) separator before the flags you’re passing through.
 ›   For example: heroku addons:create -a heroku-cli-test-staging heroku-postgresql:private-0 -- --follow
 ›   See https://devcenter.heroku.com/changelog-items/2925 for more info.

6. Once finished, remove any test provisioned addons to the aforementioned app used

[zwhitfield3]

Waiting for CX approval so that heroku-cli-command can be bumped with the latest copy. Once changes are made to the upstream dependency, this PR will be good to merge.

[k80bowman]

LGTM