Adds redshift_cross_region_snapshots module (#35527)

* add redshift_cross_region_snapshots module, unit tests.

* fix errors

* use ec2_argument_spec as the basis for the argument spec. fixed
metadata_version

* follow best practices by naming example tasks.

* code review changes

* fix linting errors

* Update version added

test/units/modules/cloud/amazon/test_redshift_cross_region_snapshots.py

@@ -0,0 +1,48 @@
+from ansible.modules.cloud.amazon import redshift_cross_region_snapshots as rcrs
+
+mock_status_enabled = {
+    'SnapshotCopyGrantName': 'snapshot-us-east-1-to-us-west-2',
+    'DestinationRegion': 'us-west-2',
+    'RetentionPeriod': 1,
+}
+
+mock_status_disabled = {}
+
+mock_request_illegal = {
+    'snapshot_copy_grant': 'changed',
+    'destination_region': 'us-west-2',
+    'snapshot_retention_period': 1
+}
+
+mock_request_update = {
+    'snapshot_copy_grant': 'snapshot-us-east-1-to-us-west-2',
+    'destination_region': 'us-west-2',
+    'snapshot_retention_period': 3
+}
+
+mock_request_no_update = {
+    'snapshot_copy_grant': 'snapshot-us-east-1-to-us-west-2',
+    'destination_region': 'us-west-2',
+    'snapshot_retention_period': 1
+}
+
+
+def test_fail_at_unsupported_operations():
+    response = rcrs.requesting_unsupported_modifications(
+        mock_status_enabled, mock_request_illegal
+    )
+    assert response is True
+
+
+def test_needs_update_true():
+    response = rcrs.needs_update(mock_status_enabled, mock_request_update)
+    assert response is True
+
+
+def test_no_change():
+    response = rcrs.requesting_unsupported_modifications(
+        mock_status_enabled, mock_request_no_update
+    )
+    needs_update_response = rcrs.needs_update(mock_status_enabled, mock_request_no_update)
+    assert response is False
+    assert needs_update_response is False