Candidates of errors to remove from PMD/spotbugs checks

[BenWhitehead]

Coming from the standpoint of Firestore samples projects

• IMC_IMMATURE_CLASS_NO_TOSTRING we usually don't have toString for many classes intentionally
• SIC_INNER_SHOULD_BE_STATIC_ANON for query watch where a callback has to be supplied (sure it could be a separate class from a type signature standpoint, but that moves the code away from the sample)
• PRMC_POSSIBLY_REDUNDANT_METHOD_CALLS the code in question is creating the initial dataset to show how queries work, and necessarily have to call the same methods a few times

[lesv]

Will be in next release