NatSpec and multiple events with identical signature

It is impossible to define multiple events with the same signature in the same contract. This lead to the design that the user documentation ("NatSpec") has a mapping of event signatures to the description of the event.

What has been possible for a while now is for a contract to emit events with the same signature but different natspec through the use of libraries or via referencing events of a different contract.. The events emitted this way were ignored in the natspec output so far.

We now have different options to solve this situation:
- change the natspec json to use arrays instead of direct objects
- only use "the first" non-empty natspec (prioritize the event in the current contract or a base and then use AST IDs for priorization)
- somehow combine the documentations (difficult for parameters etc)
- issue a warning if such a clash happens

No source files, tests, or entry points are named. First resolve which NatSpec JSON behavior should be adopted for identical event signatures—arrays, first non-empty documentation, combined documentation, or a warning—then identify the affected compiler and output tests; done means the chosen behavior is implemented and verified.

Written by the indexing model from the issue text.