Query of existing entity permissions during view permission generation
could cause timeouts or SQL placeholder limits due to massive whereOr
query generation, where an "or where" clause would be created for each
entity type/id combo involved, which could be all within 20 books.
This updates the query handling to use a query per type involved, with
no "or where"s, and to be chunked at large entity counts.
Also tweaked role-specific permission regen to chunk books at
half-previous rate to prevent such a large scope being involved on each
chunk.
For #4695
