Reland "[ffx][config] Add missing dual mode config defaults"

This is a reland of commit 6101b872cf9b4db779fe895412409dc7e08cd9dd

Triage doesn't actually have a config.json, it just looked like it from
a naive search. The other two are fine though.

Original change's description:
> [ffx][config] Add missing dual mode config defaults
>
> Adding the default config json files from product_bundle, test, and
> triage ffx subtools was missed in the migration to dual mode building.
>
> This adds them to the list so their configurations are correctly
> available.
>
> Change-Id: If0c5291b5d58285f2775ccabbe58593520bc7b7d
> Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/889014
> Reviewed-by: Andrew Davies <awdavies@google.com>
> Commit-Queue: Andrew Davies <awdavies@google.com>
> Commit-Queue: Megan Batty <mgnb@google.com>
> Reviewed-by: Steven Grady <slgrady@google.com>
> Fuchsia-Auto-Submit: Megan Batty <mgnb@google.com>

Change-Id: I068ec61cc33cb159e3f6a9499b8184a8b923c0d5
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/889171
Reviewed-by: Steven Grady <slgrady@google.com>
Commit-Queue: Megan Batty <mgnb@google.com>