Change container layer interface to accept list of env_vars (#2008)

Summary:
Pull Request resolved: #2008

X-link: facebookresearch/fbpcp#475

One of the requirements of TLS/OPA integration is to be able to send a set of env_vars for each container. Currently, the infra only supports a single set of env_vars for all containers. This stack of diffs is to enable this feature for private lift runs.

This diff:
* modify the container interface to accept a list of env_vars in addition to a single env_vars dict in `create_instances`
* this diff only changes the interface and the functionality remains the same.

Next:
* changes in onedocker layer
* changes in pcs layer (note that this would have fbpcp release dependency)

Reviewed By: liliarizona

Differential Revision: D42199006

fbshipit-source-id: d32eb53abba97e2027d3556920480d4b03bb09e6

Author: YigeZhu

fbpcs/common/service/pcs_container_service.py

@@ -61,6 +61,7 @@ def create_instance(
 
         return PCSContainerInstance.from_container_instance(instance, log_url)
 
+    # pyre-ignore[14]: Inconsistent override
     def create_instances(
         self,
         container_definition: str,