workflows: actions as templates

• Removes the tight coupling to WTForms when designing UI widgets for actions in the Holding Pen. Now jinja2 templating can be used to render the action instead.

• Removes the need to dynamically load the actions js files.

• Updates the sample "approval" action to use jinja2 templating and simplifies the accompanying js file.

• Removes much unused or unnecessary code including unfinished actions and the few defined WTForms fields that are no longer in use.

• Updates the Holding Pen page structure to be simpler as a result of merging the /actions and /details pages into one page (details).

• Updates bundles and templates to work properly with DataTables and actions.

• Adds a delayed option to BibWorkflowObject functions to start and continue workflows asynchronously.

Co-authored-by: Guillaume Lastecoueres <PX9e@gmx.fr>
Signed-off-by: Jan Aage Lavik <jan.age.lavik@cern.ch>