PathOutputCommitter to add method failedTaskAttemptCommitRecoverable()

Related to MAPREDUCE-7282 a variant solution

1. we add a new method for committers to declare whether they can recover from a task attempt commit failure
2. default = true; v2 and (external) EMR spark committers can return false

execution engine - MR, Spark, can look at this after a task attempt fails to commit and decide what to do

recoverable: execute/commit another task attempt

non-recoverable, one of (Configured)

• warn and continue
• abort the job

with the job abort option, users would be confident that if a failure happened during the commit phase, they'd know about it and choose how to recover.

I'd use a long/unusual name, so that in, say, Spark, reflection to could be used to find and call the method & so compile against older releases