Review Board includes the Djblets Pipeline bundle definitions as part of

its own definitions. This allows us to easily iterate on and build all

the Djblets static media files without making the process a completely

separate step during development. It also allows us to map bundle names

to built files, which is important in production.
Historically, the Review Board packages have contained the Djblets

static media, due to the inclusion of these bundles. This adds to the

size of the builds and the build times themselves, but goes unused in

production. When creating/updating a site, the static/djblets/

directory actually comes from the Djblets package and not Review

Board's.
So there's no reason to include them in the packages. But worse, with

the modern Babel/Rollup/TypeScript support, building Review Board

packages now fails when building against a Djblets package (such as in

CI). This is because the config files and node_modules needed by

Djblets aren't available without a Djblets source tree.
We now leave out the Djblets bundles when we're forcing static media to

build for packages (via ./setup.py bdist_wheel or

./contrib/internal/build-media.py). It's still included in all other

cases, ensuring nothing breaks when running Review Board.

Tested building packages and checking which bundles were built and

included.
Tested a site against packaged versions of Review Board and Djblets

and verified it ran.
Deployed a package built with this change to reviews.reviewboard.org

and verified nothing broke.