3.x: Ensure delegating operator overloads list all relevant @throws too in their Javadocs

[akarnokd]

The current ParamValidationNaming can only check explicit argument validation (i.e., the method body lists requireNonNull or verifyPositive) but not overloads delegating to those methods thus lacking the explicit argument validation themselves.

I don't think this can be automated, therefore, each base reactive class' source should be manually examined and expanded with the missing @throws declaration:

• Flowable
• Observable
• Maybe
• Single
• Completable
• ParallelFlowable

(There is currently an Observable cleanup PR in the works, please wait for it before doing this issue.)

Edit

Perhaps checking if the typical method parameter names, such as bufferSize, prefetch, capacityHint, source*, mapper, predicate, etc. appear in @throws declaration.