This PR is inspired by a recent code review comment on a PR that introduced new functions to the net_processing module. The point of the discussion was basically that whenever we pass something not by value (in the concrete example it was about CNode* and CConnman*) we should either use a pointer (CType*) with null pointer check or a reference (CType&) To keep things simple, this PR for a first approach only tackles CNode* pointers only within the net_processing module, i.e. no changes that would need adaption in other modules keeps the names of the variables as they are I'm aware that PRs like this are kind of a PITA to review, but I think the code quality would increase if we get rid of pointers without nullptr check -- bloating up the code by adding all the missing checks would be the worse alternative, in my opinion. Possible follow-up PRs, in case this is received well: replace CNode pointers by references for net module replace CConnman pointers by references for net_processing module ...
Backport of core PR19053.
Depends on D8469.