4269: added job validation forbidding collection uuids

Added Job validation no_collection_uuids, searching recursively through
script_parameters for any field matching a collection uuid pattern.
4269: clean up uuid regex matching

Code review feedback:

* Improved name for validation "no_collection_uuids" to
  "ensure_no_collection_uuids_in_script_params"

* Added ArvadosModel.uuid_regex (along the lines of uuid_like_pattern)
  and substituted it for hardcoded uuid regexes throughout the code.
Merge branch '4269-no-collection-uuid-in-script-params'

Refs #4269.