KAFKA-20864: Fix to avoid early batch close if extension fails

[lianetm]

This PR includes the following fixes to avoid closing the wrong batch
when a mid-batch extension acquire fails on an exhausted pool:

• close the batch only if it's the same we were trying to extend. If
  it's not, do not close it and continue the loop, so the next iteration
  checks against whatever is open (will take the new-batch path if
  nothing is open, or retry with the new open batch, sizing the extension
  needed again)
• bound the retries the above introduces (retry of non-blocking op). Fix
  by always allowing a first attempt (it's non-blocking), but bound
  retries against the remaining max.block.ms. Edge case to ensure send
  does not exceed max.block.ms if the extension keeps failing with the
  batch being replaced.
• track an absolute deadline, so that the non-blocking retries time also
  count against max.block.ms (like the blocking ops do)