HADOOP-18104: S3A: Add configs to configure minSeekForVectorReads and maxReadSizeForVectorReads (#3964)

Part of HADOOP-18103.
Introducing fs.s3a.vectored.read.min.seek.size and fs.s3a.vectored.read.max.merged.size
to configure min seek and max read during a vectored IO operation in S3A connector.
These properties actually define how the ranges will be merged. To completely
disable merging set fs.s3a.max.readsize.vectored.read to 0.

Contributed By: Mukund Thakur
11 files changed