Add enough BUILD files to make it possible to
`bazel build packages/core/test`
Also re-format BUILD.bazel files with Buildifier.
Add a CI lint check that they stay formatted.
PR Close#20768
This fixes a flicker when transitioning from server rendered page to client rendered page in lazy loaded routes by waiting for the lazy loaded route to finish loading, assuming initialNavigation on the route is set to 'enabled'.
Fixes#15716
Alex Eagle
Victor Berchet
vikerman
Jason Aden