Support more filtering on event types

[lukerosser]

At the moment the event types can only be filtered as "all" or "issue":

https://github.com/aws-samples/aws-health-aware/blob/main/handler.py#L646-L649

It should be possible to filter these more granularly: https://docs.aws.amazon.com/health/latest/APIReference/API_EventType.html

Request to allow passing in any combination of valid event types to filter on

[neilfarmer]

I would like to see this functionality enabled as well specifically to exclude certain events.

I have an environment of 100+ accounts and support numerous internal teams. AHA (Terraform provisioned) is being used to centrally show events/issues via slack to all my internal teams. I see a lot of notifications about Cloudshell expirations and would like to be able to exclude these from showing up in slack (or any other messaging service). These Cloudshell notifications are noisy.

Thanks for making this tool, its pretty awesome and easy to setup!

-Neil