[roll] Roll fuchsia [fxtest] Publish manifests with "incremental" feature

When running `fx test` with the "incremental" fx feature to enable
incremental publishing, was possible that `fx test` could rebuild the
test packages, then trigger the test before the incremental publisher
had published all the packages.  When that happened, the test could end
up running the old version of the test packages.

Ideally the incremental publisher would have a way to block until the
publishing happened, but that feature doesn't exist yet. As a stopgap,
this patch changes `fx test` to publish the test package manifests after
the build has completed. This shouldn't corrupt the repository because
`package-tool` grabs the repository lock before we make any changes to
it.

However, while this protects us from running the tests before they've
been published, we could still run into races if the components in the
test packages depend on any other packages, since those dependencies
would not show up in the `tests.json`.

Fortunately, it seems a large percentage of test packages don't have
these dependencies, so this should reduce the races users may encounter
before we have a proper incremental publishing barrier implemented.

Original-Bug: 107343
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/811270
Original-Revision: 6a2dae738d88ae4d0ed2936ed717a7ce795b686f
GitOrigin-RevId: 4e65ce8c1ff98eb5cbacad22dcf17a1aef166c45
Change-Id: I81c21ce168464642049e78d736988198b6d4875e