Test for shuffle requests packaging with different size and numBlocks limit

When packaging shuffle fetch requests in ShuffleBlockFetcherIterator, there are two limitations: maxBytesInFlight and maxBlocksInFlightPerAddress. However, we don’t have test cases to test them both, e.g. the size limitation is hit before the numBlocks limitation.

We should add test cases in ShuffleBlockFetcherIteratorSuite to test:

1. the size limitation is hit before the numBlocks limitation

1. the numBlocks limitation is hit before the size limitation