* 6.x:
  SQL: Fix build on Java 10
  [Tests] Mutualize fixtures code in BaseHttpFixture (#31210)
  [TEST] Fix RemoteClusterClientTests#testEnsureWeReconnect
  [ML] Update test thresholds to account for changes to memory control (#31289)
  Reenable Checkstyle's unused import rule (#31270)
  [ML] Check licence when datafeeds use cross cluster search  (#31247)
  Fix non-REST doc snippet
  [DOC] Extend SQL docs
  [DOCS] Shortens ML API intros
  Use quotes in the call invocation (#31249)
  move security ingest processors to a sub ingest directory (#31306)
  SQL: Whitelist SQL utility class for better scripting (#30681)
  Add 5.6.11 version constant.
  Fix version detection.
  [Docs] All Rollup docs experimental, agg limitations, clarify DeleteJob (#31299)
  Add missing release notes.
  Security: fix token bwc with pre 6.0.0-beta2 (#31254)
  Fix compilation error in UpdateSettingsIT (#31304)
  Test: Remove broken yml test feature (#31255)
  Add unreleased version 6.3.1
  [Rollup] Metric config parser must use builder so validation runs (#31159)
  Removes experimental tag from scripted_metric aggregation (#31298)
  [DOCS] Removes coming tag from 6.3.0 release notes
  6.3 release notes.
  Add notion of internal index settings (#31286)
  REST high-level client: add Cluster Health API (#29331)
  Remove leftover usage of deprecated client API
  SyncedFlushResponse to implement ToXContentObject (#31155)
  Add Get Aliases API to the high-level REST client (#28799)
  HLRest: Add get index templates API (#31161)
  Log warnings when cluster state publication failed to some nodes (#31233)
  Fix AntFixture waiting condition (#31272)
  [TEST] Mute RecoveryIT.testHistoryUUIDIsGenerated
  Ignore numeric shard count if waiting for ALL (#31265)
  Update checkstyle to 8.10.1 (#31269)
  Set analyzer version in PreBuiltAnalyzerProviderFactory (#31202)
  Revert upgrade to Netty 4.1.25.Final (#31282)
  Use armored input stream for reading public key (#31229)
  [DOCS] Added 'fail_on_unsupported_field' param to MLT. Closes #28008 (#31160)
  Fix Netty 4 Server Transport tests. Again.
  [DOCS] Fixed typo.
  [DOCS] Added release highlights for 6.3 (#31256)
  [DOCS] Mark SQL feature as experimental
  [DOCS] Updates machine learning custom URL screenshots (#31222)
  Fix naming conventions check for XPackTestCase
  Fix security Netty 4 transport tests
  Fix race in clear scroll (#31259)
  [DOCS] Clarify audit index settings when remote indexing (#30923)
  [ML][TEST] Mute tests using rules (#31204)
  Support RequestedAuthnContext (#31238)
  Validate xContentType in PutWatchRequest. (#31088)
  [INGEST] Interrupt the current thread if evaluation grok expressions take too long (#31024)
  Upgrade to Netty 4.1.25.Final (#31232)
  Suppress extras FS on caching directory tests
  Revert "[DOCS] Added 6.3 info & updated the upgrade table. (#30940)"
  Revert "Fix snippets in upgrade docs"
  Fix snippets in upgrade docs
  [DOCS] Added 6.3 info & updated the upgrade table. (#30940)
  Enable custom credentials for core REST tests (#31235)
  Move ESIndexLevelReplicationTestCase to test framework (#31243)
  Encapsulate Translog in Engine (#31220)
  [DOCS] Adds machine learning 6.3.0 release notes (#31217)
  Remove all unused imports and fix CRLF (#31207)
  [TEST] Fix testRecoveryAfterPrimaryPromotion
  [Docs] Remove mention pattern files in Grok processor (#31170)
  Use stronger write-once semantics for Azure repository (#30437)
  Don't swallow exceptions on replication (#31179)
  Compliant SAML Response destination check (#31175)
  Move java version checker back to its own jar (#30708)
  TEST:  Retry synced-flush if ongoing ops on primary (#30978)
  [test] add fix for rare virtualbox error (#31212)