Add view handling to query engine and planner

[joshua-spacetime]

Description of Changes

This patch does the following:

1. Expands views as part of query planning. Views are always assumed to be materialized by the query planner, however a view's backing table may have private columns such as the sender column. The query planner needs to filter by this column in order to select the rows pertaining to a particular caller.
2. Plumbs AuthCtx through the query optimizer. This is needed in order to implement (1).
3. Adds a new operator for views to the query engine that drops a view's private columns

API and ABI breaking changes

None

Expected complexity level and risk

2.5

Testing

• SQL http tests
• Subscription tests
• One off query tests