[kernel][lib] Systematize GN deps for tests

This establishes a new protocol for GN target names defined by
every subdirectory of //zircon/kernel/lib, and also by lib itself
and //zircon/kernel/tests and //zircon/kernel itself.  Each of
the four sorts of tests (userland/host, kernel, phys, and boot)
has a mandatory target in each subdirectory.  This should avoid
future regressions or omissions in plumbing all the test groups.

Change-Id: Id0df194252d30a8a8213a45f3e894b9d061cfaf1
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1387062
Fuchsia-Auto-Submit: Roland McGrath <mcgrathr@google.com>
Reviewed-by: Marco Vanotti <mvanotti@google.com>
Reviewed-by: Nick Maniscalco <maniscalco@google.com>
Commit-Queue: Roland McGrath <mcgrathr@google.com>
67 files changed