feat: welcome presto to the suite of tested databases (#10498)

* Add presto to the CI

Sample test data

Datetime conversion

Sample test data

Fix tests

* TODO to switch to timestamps

* Address feedback

* Update requirements

* Add TODOs

Co-authored-by: bogdan kyryliuk <bogdankyryliuk@dropbox.com>

superset/utils/core.py

@@ -1022,6 +1022,13 @@ def get_example_database() -> "Database":
     return get_or_create_db("examples", db_uri)
 
 
+def get_main_database() -> "Database":
+    from superset import conf
+
+    db_uri = conf.get("SQLALCHEMY_DATABASE_URI")
+    return get_or_create_db("main", db_uri)
+
+
 def is_adhoc_metric(metric: Metric) -> bool:
     return bool(
         isinstance(metric, dict)