Merge remote-tracking branch 'remotes/armbru/tags/pull-qapi-2021-08-26' into staging

Merge remote-tracking branch 'remotes/armbru/tags/pull-qapi-2021-08-26' into staging

QAPI patches patches for 2021-08-26

# gpg: Signature made Thu 26 Aug 2021 13:18:34 BST
# gpg:                using RSA key 354BC8B3D7EB2A6B68674E5F3870B400EB918653
# gpg:                issuer "armbru@redhat.com"
# gpg: Good signature from "Markus Armbruster <armbru@redhat.com>" [full]
# gpg:                 aka "Markus Armbruster <armbru@pond.sub.org>" [full]
# Primary key fingerprint: 354B C8B3 D7EB 2A6B 6867  4E5F 3870 B400 EB91 8653

* remotes/armbru/tags/pull-qapi-2021-08-26:
  qapi: make 'if' condition strings simple identifiers
  qapi: add 'not' condition operation
  qapi: Use 'if': { 'any': ... } where appropriate
  qapi: add 'any' condition
  qapi: replace if condition list with dict {'all': [...]}
  qapidoc: introduce QAPISchemaIfCond.docgen()
  qapi: introduce QAPISchemaIfCond.cgen()
  qapi: add QAPISchemaIfCond.is_present()
  qapi: wrap Sequence[str] in an object
  docs: update the documentation upfront about schema configuration
  qapi: Fix crash on redefinition with a different condition

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