Upgrade extended info in SQL lease database

Define a new Lease Query hook command which upgrade extended info in SQL lease database (can do nothing with memfile because this operation is performed during the loading phase).

Note this can be done in parallel with server service because all changes are done using current settings. Standard update can be used, only the retrieval should use a specialized version of GET_LEASEx_PAGE to filter out leases with NULL user_context.

Proposed parameter: size of the page (but progress will be visible only in debug logs).

Depends on #2752 (closed) and perhaps also on #2753 (closed), related to #2623 (closed)