Merge remote-tracking branch 'remotes/qmp-unstable/queue/qmp' into staging

Merge remote-tracking branch 'remotes/qmp-unstable/queue/qmp' into staging

* remotes/qmp-unstable/queue/qmp:
  qapi: skip redundant includes
  monitor: Add netdev_del id argument completion.
  monitor: Add netdev_add type argument completion.
  monitor: Add set_link arguments completion.
  monitor: Add chardev-add backend argument completion.
  monitor: Add chardev-remove command completion.
  monitor: Convert sendkey to use command_completion.
  qapi: Show qapi-commands.py invocation in qapi-code-gen.txt
  qapi: Replace uncommon use of the error API by the common one
  tests: Don't call visit_end_struct() after visit_start_struct() fails
  hw: Don't call visit_end_struct() after visit_start_struct() fails
  hmp: Call visit_end_struct() after visit_start_struct() succeeds
  qapi: Un-inline visit of implicit struct
  qapi-visit.py: Clean up a sloppy use of field prefix
  qapi: Clean up shadowing of parameters and locals in inner scopes
  qapi-visit.py: Clean up confusing push_indent() / pop_indent() use
  qapi: Replace start_optional()/end_optional() by optional()
  qapi: Remove unused Visitor callbacks start_handle(), end_handle()
  qapi: Normalize marshalling's visitor initialization and cleanup
  qapi: Update qapi-code-gen.txt example to match current code

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