Merge remote-tracking branch 'remotes/maxreitz/tags/pull-block-2021-01-26' into staging

Merge remote-tracking branch 'remotes/maxreitz/tags/pull-block-2021-01-26' into staging

Block patches:
- Make backup block jobs use asynchronous requests with the block-copy
  module
- Use COR filter node for stream block jobs
- Make coroutine-sigaltstack’s qemu_coroutine_new() function thread-safe
- Report error string when file locking fails with an unexpected errno
- iotest fixes, additions, and some refactoring

# gpg: Signature made Tue 26 Jan 2021 14:16:59 GMT
# gpg:                using RSA key 91BEB60A30DB3E8857D11829F407DB0061D5CF40
# gpg:                issuer "mreitz@redhat.com"
# gpg: Good signature from "Max Reitz <mreitz@redhat.com>" [full]
# Primary key fingerprint: 91BE B60A 30DB 3E88 57D1  1829 F407 DB00 61D5 CF40

* remotes/maxreitz/tags/pull-block-2021-01-26: (53 commits)
  iotests/178: Pass value to invalid option
  iotests/118: Drop 'change' test
  iotests: Add test for the regression fixed in c8bf9a9169
  block: report errno when flock fcntl fails
  simplebench: add bench-backup.py
  simplebench: bench_block_job: add cmd_options argument
  simplebench/bench_block_job: use correct shebang line with python3
  block/block-copy: drop unused argument of block_copy()
  block/block-copy: drop unused block_copy_set_progress_callback()
  qapi: backup: disable copy_range by default
  backup: move to block-copy
  block/backup: drop extra gotos from backup_run()
  block/block-copy: make progress_bytes_callback optional
  iotests: 257: prepare for backup over block-copy
  iotests: 219: prepare for backup over block-copy
  iotests: 185: prepare for backup over block-copy
  iotests/129: Limit backup's max-chunk/max-workers
  iotests: 56: prepare for backup over block-copy
  qapi: backup: add max-chunk and max-workers to x-perf struct
  job: call job_enter from job_pause
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>