Fix a number of issues related to project resource traversal

[ryanjjung]

This PR addresses a few main issues.

1. Can't declare recovery_window_in_days for Secret created by RdsDatabaseGroup #70: When volatile environments using the RDS module are rebuilt, you run into Secrets Manager clobbers. This PR allows you to optionally change the retention period on those secrets to prevent this issue in some environments while allowing the protection of this retention feature in others.
2. ThunderbirdPulumiProject doesn't flatten resources hidden behind outputs #71: Resources hidden by Pulumi Output objects do not get enumerated properly by monitoring groups.
3. ThunderbirdComponentResources create namespace pollution in project #72: When ThunderbirdComponentResources register their resources with the project, it can cause namespace pollution.
4. Updates the AWS provider.

The issues have much more detail about the problems than I've listed here. A good chunk of this is corresponding documentation updates.