[sdk][modular] Migrate //sdk/modular from package()

Migrates //sdk/modular/* to the new package build rules.

Change-Id: Ia4fce02ce76ad875a1e279ff93d774f621c7eb97
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/484180
Commit-Queue: John Shamoon <johnshamoon@google.com>
Reviewed-by: Vardhan Mudunuru <vardhan@google.com>
Reviewed-by: Yegor Pomortsev <ypomortsev@google.com>
Reviewed-by: Kevin Lindkvist <lindkvist@google.com>