(cherry picked from commit 8b698f0)

* elastic/master: (92 commits)
  Reduce number of raw types warnings (elastic#31523)
  Migrate scripted metric aggregation scripts to ScriptContext design (elastic#30111)
  turn GetFieldMappingsResponse to ToXContentObject (elastic#31544)
  Close xcontent parsers (partial) (elastic#31513)
  Ingest Attachment: Upgrade Tika to 1.18 (elastic#31252)
  TEST: Correct the assertion arguments order (elastic#31540)
  Add get field mappings to High Level REST API Client (elastic#31423)
  [DOCS] Updates Watcher examples for code testing (elastic#31152)
  TEST: Add bwc recovery tests with synced-flush index
  [DOCS] Move sql to docs (elastic#31474)
  [DOCS] Move monitoring to docs folder (elastic#31477)
  Core: Combine doExecute methods in TransportAction (elastic#31517)
  IndexShard should not return null stats (elastic#31528)
  fix repository update with the same settings but different type (elastic#31458)
  Fix Mockito trying to mock IOException that isn't thrown by method (elastic#31433) (elastic#31527)
  Node selector per client rather than per request (elastic#31471)
  Core: Combine messageRecieved methods in TransportRequestHandler (elastic#31519)
  Upgrade to Lucene 7.4.0. (elastic#31529)
  [ML] Add ML filter update API (elastic#31437)
  Allow multiple unicast host providers (elastic#31509)
  ...

* 6.x:
  Fix broken backport of #31578 by adjusting constructor (#31587)
  ingest: Add ignore_missing property to foreach filter (#22147) (#31578)
  Add package pre-install check for java binary (#31343)
  Docs: Clarify sensitive fields watcher encryption (#31551)
  Watcher: Remove never executed code (#31135)
  Improve test times for tests using `RandomObjects::addFields` (#31556)
  Revert "Remove RestGetAllAliasesAction (#31308)"
  REST high-level client: add simulate pipeline API (#31158)
  Get Mapping API to honour allow_no_indices and ignore_unavailable (#31507)
  Fix Mockito trying to mock IOException that isn't thrown by method (#31433) (#31527)
  [Test] Add full cluster restart test for Rollup (#31533)
  Enhance thread context uniqueness assertion
  fix writeIndex evaluation for aliases (#31562)
  Add x-opaque-id to search slow logs (#31539)
  Watcher: Fix put watch action (#31524)
  [DOCS] Significantly improve SQL docs
  turn GetFieldMappingsResponse to ToXContentObject (#31544)
  TEST: Unmute testHistoryUUIDIsGenerated
  Ingest Attachment: Upgrade Tika to 1.18 (#31252)
  TEST: Correct the assertion arguments order (#31540)

* master:
  ingest: Add ignore_missing property to foreach filter (#22147) (#31578)
  Fix a formatting issue in the docvalue_fields documentation. (#31563)
  reduce log level at gradle configuration time
  [TEST] Close additional clients created while running yaml tests (#31575)
  Docs: Clarify sensitive fields watcher encryption (#31551)
  Watcher: Remove never executed code (#31135)
  Add support for switching distribution for all integration tests (#30874)
  Improve robustness of geo shape parser for malformed shapes (#31449)
  QA: Create xpack yaml features (#31403)
  Improve test times for tests using `RandomObjects::addFields` (#31556)
  [Test] Add full cluster restart test for Rollup (#31533)
  Enhance thread context uniqueness assertion
  [DOCS] Fix heading format errors (#31483)
  fix writeIndex evaluation for aliases (#31562)
  Add x-opaque-id to search slow logs (#31539)
  Watcher: Fix put watch action (#31524)
  Add package pre-install check for java binary (#31343)
  Reduce number of raw types warnings (#31523)
  Migrate scripted metric aggregation scripts to ScriptContext design (#30111)
  turn GetFieldMappingsResponse to ToXContentObject (#31544)
  Close xcontent parsers (partial) (#31513)
  Ingest Attachment: Upgrade Tika to 1.18 (#31252)
  TEST: Correct the assertion arguments order (#31540)