aws - ssm - session-manager-regional-settings support

[mattheidelbaugh]

Closes #9386, #9535

[thisisshi]

Let's actually do a value filter here maybe of type: content so that we can do arbitrary filters on the values inside the document:

policies:
- name: ssm-doc-content-filter
  resource: aws.ssm-document
  filters:
     - type: content
        key: foo
        value: bar

[kapilt]

as noted in the community call, this should really be more of a separate content filter on documents, rather then augment to avoid extra api calls for use cases where the content is not the focus, ie tag policies for example.