Run integration test PR checks nightly (#2222)

* Run integration test PR checks nightly

Scheduled for 5AM UTC. This will assist in catching bugs introduced with new runner images.

* Specify generated YAML indentations

For consistency with our non-autogenerated files and GitHub documentation, we should further indent items in lists (`sequence`).

pr-checks/sync.py

@@ -1,7 +1,7 @@
 #!/usr/bin/env python
 
 import ruamel.yaml
-from ruamel.yaml.scalarstring import FoldedScalarString
+from ruamel.yaml.scalarstring import FoldedScalarString, SingleQuotedScalarString
 import pathlib
 import textwrap
 
@@ -46,6 +46,7 @@ def writeHeader(checkStream):
 
 yaml = ruamel.yaml.YAML()
 yaml.Representer = NonAliasingRTRepresenter
+yaml.indent(mapping=2, sequence=4, offset=2)
 
 this_dir = pathlib.Path(__file__).resolve().parent
 
@@ -157,6 +158,7 @@ for file in (this_dir / 'checks').glob('*.yml'):
                 'pull_request': {
                     'types': ["opened", "synchronize", "reopened", "ready_for_review"]
                 },
+                'schedule': [{'cron': SingleQuotedScalarString('0 5 * * *')}],
                 'workflow_dispatch': {}
             },
             'jobs': {