feat: add rql query creators for workflowable entities

This adds three workflow related rql query creators.
They return a bound rql query (a tuple [query, vars]) directly usable
with transactionV2.
The result extraction is left to the user but is documented for each
query.
We could add a wrapper doing the query and extraction later but I don't
know which form it could take.

Closes #3.
4 jobs for topic/default/workflow-rql-queries in 2 minutes and 35 seconds (queued for 5 seconds)
Status Job ID Name Coverage
  Deps
passed Deps #80121

00:01:38

 
  Test
passed CanBuild #80124

00:00:56

passed Format #80123

00:00:41

passed Lint #80122

00:00:48