11907: Make collections containing dependencies have predictable PDHs

11907: Make collections containing dependencies have predictable PDHs

Removes optimization that tries to avoid redundant file
uploads (decided complexity tradeoff isn't worth it.)  Collections
created from local file inputs longer use block packing.

Likely to invalidate job reuse for jobs submitted by past versions of
a-c-r, but will have more stable job reuse going forward.

Arvados-DCO-1.1-Signed-off-by: Peter Amstutz <pamstutz@veritasgenetics.com>