[PF-504] Remove workspace editor role, give its permissions to writers

[zloery]

Ticket: PF-504

This ticket removes the recently added editor role from workspace objects and instead grants its permissions around child resources to the writer role. This is more in line with existing Rawls behavior, and will simplify future migrations. In the future, we may add an additional workspace role for "modifying objects without creating or deleting", which was previously the writer role.

I've intentionally left the editor role in all four controlled resource definitions. It's different than the workspace editor role, and separating delete permission from read/write permission is core to our model of private resources.

---

PR checklist

• I've followed the instructions if I've made any changes to the API, especially if they're breaking changes
• I've filled out the Security Risk Assessment and attached the result to the JIRA ticket

[coveralls]

Coverage remained the same at 78.54% when pulling df1fa4c on wsm-editor into d730e23 on develop.

[ddietterich]

lgtm

[ddietterich]

lgtm