Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging

Block layer patches:

- Fix crash on write to read-only devices
- iotests: Rewrite 'check' in Python, get rid of 'groups' and allow
  non-numeric test case names

# gpg: Signature made Wed 27 Jan 2021 19:56:00 GMT
# gpg:                using RSA key DC3DEB159A9AF95D3D7456FE7F09B272C88F2FD6
# gpg:                issuer "kwolf@redhat.com"
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>" [full]
# Primary key fingerprint: DC3D EB15 9A9A F95D 3D74  56FE 7F09 B272 C88F 2FD6

* remotes/kevin/tags/for-upstream:
  iotests: rename and move 169 and 199 tests
  iotests: rewrite check into python
  iotests: add testrunner.py
  iotests: add testenv.py
  iotests: add findtests.py
  iotests: 146: drop extra whitespaces from .out file
  virtio-scsi-test: Test writing to scsi-cd device
  block: Separate blk_is_writable() and blk_supports_write_perm()

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

diff --cc docs/devel/testing.rst
Simple merge