Add support for cloudwatch logs resource policies

[stiak]

Issue #, if available: https://github.com/aws-cloudformation/aws-cloudformation-coverage-roadmap/issues/249

Description of changes: This adds a AWS::Logs::ResourcePolicy type.

A few questions that I need help to answer:

• ~I have modelled a Name attribute, though the API uses PolicyName. Any preferences?~ It's PolicyName to match
• The policy document is actually JSON, but I'm not sure how to specify a JSON type. Should I leave it as a string, or is there some better handling I should be doing? The API object also has it as a string so I guess there is some server side validation that would happen.
• ~It seems like the create should fail if a policy already exists with the same name. I started writing a test and implementation for that, but need some pointers on how to best retrieve existing policies with DescribeResourcePoliciesResponse. Test remains as commented out code.~ I used the approach from metric filter.
• ~Update should fail if the resource doesn't already exist (according to the FAQ). I need help understanding how to access the API client to do this check.~ I've used the approach from metric filters to access the API.
• ~I started with the query definitions as a reference implementation, but realised that isn't live yet. Would metricfilter be a better starting point?~ I've mixed and matched from both.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[adamcrosby]

I'd prefer keeping attribute names identical - its a source of consistent frustration when they change between representations, given how much documentation is auto-generated/etc. So, PolicyName would be preferred.

And thank you for taking this on, we literally just ran into this today and had to rethink a ton of stuff now that we can't do 'native' cfn for our project.

[sfbaker7]

+1 on adamcrosby's comment - thanks for taking this up. I left some comments.

Also, when you have a change, can you paste your integration test + contract test results? LMK if you have any questions about running these, you can also check out the walk through here: https://docs.aws.amazon.com/cloudformation-cli/latest/userguide/resource-type-walkthrough.html#resource-type-walkthrough-test

[stiak]

contract-test-output.txt I had a few runs but there always seemed to be some that timed out. It's also really painfully slow...

[stiak]

Ah, found the --warm-containers EAGER option. Much better. Requests take 250ms instead of 13.5 seconds.

contract-test-output.txt

[stiak]

Updated output from contract tests (15 passed, 1 skipped).

contract-test-output.txt

I think I've addressed all the feedback now, let me know if there's anything else I should follow up on.

[sfbaker7]

looks good, thanks for contributing @stiak