Increase ECS_CONTAINER_CREATE_TIMEOUT to 10m to mitigate Docker timeouts

Many jobs were failing to start from an error:

DockerTimeoutError: Could not transition to created; timed out after waiting 4m0s

Try to mitigate this by increasing the Docker timeout from the default 4m to 10m.
ECS_CONTAINER_CREATE_TIMEOUT is not documented in the AWS developer guide, but
it does seem to be a real setting from the ECS agent repo README:
a5f8d25f66/README.md

serverless-resources.yml

@@ -84,6 +84,11 @@ rBuildsEcsLaunchTemplate:
           Ebs:
             VolumeType: gp3
             VolumeSize: 96
+      UserData:
+        Fn::Base64: |
+          #!/bin/bash
+          # Mitigate DockerTimeoutError errors from the default timeout of 4m
+          echo "ECS_CONTAINER_CREATE_TIMEOUT=10m" >> /etc/ecs/ecs.config
 
 rBuildsBatchComputeEnvironment:
   Type: AWS::Batch::ComputeEnvironment