Use enum in ProcessConfig.setRuntimeStrategy() method

Currently this method:

https://github.com/kiegroup/droolsjbpm-integration/blob/7.11.x/kie-server-parent/kie-server-controller/kie-server-controller-api/src/main/java/org/kie/server/controller/api/model/spec/ProcessConfig.java#L62

accepts a string as a parameter, which is a bit error prone.

Please provide another method (keep the current one to preserve backward compatibility) which would accept following as a parameter:

https://github.com/kiegroup/droolsjbpm-knowledge/blob/master/kie-internal/src/main/java/org/kie/internal/runtime/conf/RuntimeStrategy.java