Add force_ctas_schema to query model when enabled

[vera-liu]

Before:

• force_ctas_schema is not passed to Query model when enabled, the output column of Query Table does not receive schema from backend unless it is set in query editor

After:

• when force_ctas_schema is set, it gets stored in query, and will be displayed in output column of QueryHistory if the query was run using ctas

Tested in staging:

• Use case one: run query with selected schema in left pane

1. set schema in sql editor left pane
2. run a query
3. schema is shown in output column of Query History

• Use case two: run query with ctas on a database with force_ctas_schema

1. set schema in database view
2. run a query using ctas
3. schema.table_name is shown in output column of Query History

• Use case three: run query with selected schema and ctas

1. set schema in sql editor left pane
2. run a query using ctas
3. schema.table_name is shown in output column of Query History

Todo:

• https://github.com/airbnb/superset/issues/1850
  needs-review @bkyryliuk @mistercrunch

[bkyryliuk]

I am afraid it could break sql lab.
schema for this endpoint should be one selected in the drop down menu.
mydb.force_ctas_schema needs to be passed to the select * query that is created to get the results of the cta query I believe.

[bkyryliuk]

@vera-liu - please add a test plan to features
it simplifies the review process and explains how the feature was tested

[vera-liu]

Added @bkyryliuk

[vera-liu]

After discussing with Max, I add schema to temp_table_name before adding query, so that the actual schema used is shown in output column of Query History. PTAL @bkyryliuk

[bkyryliuk]

please add a comment that tmp_table_name includes schema here

[bkyryliuk]

could u please add a unit test to the celery tests?

[bkyryliuk]

LGTM