remove 'err' names from function return arguments in queriers

[fedekunze]

Originally posted by @rigelrozanski in #2565

Ref: #2565 (comment)

queriable.go uses err2/errRes for the error return values. For consistency let's use only err everywhere

[alexanderbez]

Yes pweeeez 🙌

Also, we should remove named return variables where it's obviously clear what the context is and the function/method is concise.

[tac0turtle]

@fedekunze & @alexanderbez has then been solved, seems the PR from 4ever9 solved most to all of them