Potential arithmetic overflow in Generator#nextAuctionLengthMs()

[kennknowles]

    long numEventsForAuctions =
        (config.configuration.numInFlightAuctions * GeneratorConfig.PROPORTION_DENOMINATOR)

       / GeneratorConfig.AUCTION_PROPORTION;

The multiplication is done on 32-bit integers while long is expected (numEventsForAuctions).

There is possibility for arithmetic overflow

Imported from Jira BEAM-2805. Original Jira may contain additional context.
Reported by: yuzhihong@gmail.com.