Switch to configurable, scaling approach to Selenium timeouts.

Implement different "WAIT_TYPES" and try to sleep for different amounts of time based on what is being waited for.

Replace sleep statements in addition to Selenium wait on statements.

test/selenium_tests/test_workflow_run.py

@@ -1,5 +1,3 @@
-import time
-
 from ._workflow_fixtures import (
     WORKFLOW_SIMPLE_CAT_TWICE,
     WORKFLOW_WITH_OLD_TOOL_VERSION,
@@ -38,6 +36,6 @@ class WorkflowRunTestCase(SeleniumTestCase, UsesHistoryItemAssertions):
 
         self.workflow_index_open()
         self.workflow_index_click_option("Run")
-        time.sleep(.5)
+        self.sleep_for(self.wait_types.UX_TRANSITION)
         # Check that this tool form contains a warning about different versions.
         self.assert_warning_message(contains="different versions")