Improve PubSub subscriber example (#1811)
Improve PubSub subscriber example (#1811)

* PubSub: Fix memleaks in subscriber tutorial

* PubSub: Stack-allocate in the subscriber tutorial

* PubSub: In subscriber tutorial, evaluate receive error code; quit early

* PubSub: In subscriber example, use logging API instead of printf

* PubSub: Reduce the max indendation of the subscriber example; Add comments

* PubSub: Use short blocking wait times in subscriber example

* PubSub: Reduce the max line length in the subscriber example

JGrothoff/open62541,jpfr/open62541,open62541/open62541,open62541/open62541,StalderT/open62541,jpfr/open62541,JGrothoff/open62541,jpfr/open62541,open62541/open62541,StalderT/open62541,StalderT/open62541,JGrothoff/open62541,open62541/open62541,jpfr/open62541,JGrothoff/open62541,StalderT/open62541