Add custom fields to reports directly within the policy yaml

[nitrocode]

Describe the feature

I am always frustrated when I have to recall a specific field for a specific policy that I need to report on.

https://cloudcustodian.io/docs/quickstart/advanced.html

It would be nice if I could codify the field itself within the policy so I can run my reports without having to recall the specific command or without having to run different commands per report.

e.g. instead of this

custodian report -s . \
  --field "AccessKey1LastRotated"='"c7n:credential-report".access_keys[0].last_rotated' \
  policies/iam-unused.yml

I can add this to my policy

policies:
  - name: iam-deactivate-old-keys
    resource: iam-user
    conditions:
      - region: us-east-1
+   report:
+     default_fields: true
+     fields:
+       - key: AccessKey1LastRotated
+         value: "\"c7n:credential-report\".access_keys[0].last_rotated"
    filters:
      - type: credential
        key: access_keys.active
        value: true
        op: eq
      - type: credential
        key: access_keys.last_rotated
        value_type: age
        value: 30
        op: greater-than
      - type: credential
        key: access_keys.last_used_date
        value_type: age
        value: 365
        op: greater-than
      # Workaround in https://github.com/cloud-custodian/cloud-custodian/issues/5583#issuecomment-1603010775
      - type: value
        key: length("c7n:matched-keys")
        value: 1
        op: gte

and simply run the report bare

custodian report -s . policies/iam-unused.yml

Extra information or context

No response