Support schema permissions (#8219)

* Build support for schema access in Superset and SQLab

* Lint
* Test for old and new flask
* Black formatting
* Cleanup modified files
* Support schema permissions
* Add migration
* Make it work for slices as well
* TODO and remove unused field
* Apply schema access check to dashboards as well

Cleaner schema permissions check

Fetch schema permissions in 1 query

Bugfix

Better datasource check

Use security manager for permissions checks and remove dead code

Properly handle anon user

Add database permissions on the database updates

Fix schema filtering

Lint / flake changes

Increase cypress request timeout

Run black

Resolve multiple alembic heads

* Use set comprehensions

* Fixes for the pylint

superset/connectors/base/models.py

@@ -61,6 +61,7 @@ class BaseDatasource(AuditMixinNullable, ImportMixin):
     cache_timeout = Column(Integer)
     params = Column(String(1000))
     perm = Column(String(1000))
+    schema_perm = Column(String(1000))
 
     sql: Optional[str] = None
     owners: List[User]