operator: specify resource requirements for operator pod

[pohly]

operator-sdk 1.16.0 adds a new "best practices" check. That one warns about our bundle:

$ _work/bin/operator-sdk bundle validate --select-optional=name=good-practices deploy/olm-bundle/1.0.2/
WARN[0000] Warning: Value pmem-csi-operator.v1.0.2: unable to find the resource requests for the container: (pmem-csi-operator). It is recommended to ensure the resource request for CPU and Memory. Be aware that for some clusters configurations it is required to specify requests or limits for those values. Otherwise, the system or quota may reject Pod creation. More info: https://master.sdk.operatorframework.io/docs/best-practices/managing-resources/ 
INFO[0000] All validation tests have completed successfully 

[pohly]

Once this warning is fixed, we probably should treat warnings as validation failures.