Get mappings HEAD requests incorrectly return a content-length header of
0. This commit addresses this by removing the special handling for get
mappings HEAD requests, and just relying on the general mechanism that
exists for handling HEAD requests in the REST layer.

* master: (1210 commits)
  Add support for clear scroll to high level REST client (elastic#25038)
  Tiny correction in inner-hits.asciidoc (elastic#25066)
  Added release notes for 6.0.0-alpha2
  Expand index expressions against indices only when managing aliases (elastic#23997)
  Collapse inner hits rest test should not skip 5.x
  Settings: Fix secure settings by prefix (elastic#25064)
  add `exclude_keys` option to KeyValueProcessor (elastic#24876)
  Test: update missing body tests to run against versions >= 5.5.0
  Track EWMA[1] of task execution time in search threadpool executor
  Removes an invalid assert in resizing big arrays which does not always hold (resizing can result in a smaller size than the current size, while the assert attempted to verify the new size is always greater than the current).
  Fixed NPEs caused by requests without content. (elastic#23497)
  Plugins can register pre-configured char filters (elastic#25000)
  Build: Allow preserving shared dir (elastic#24962)
  Tests: Make secure settings available from settings builder for tests (elastic#25037)
  [TEST] Skip wildcard expansion test due to breaking change
  Test that gradle and Java version types match (elastic#24943)
  Include duplicate jar when jarhell check fails
  Change ScriptContexts to use needs instead of uses$. (elastic#25036)
  Change `has_child`, `has_parent` queries and `childen` aggregation to work with the new join field type and at the same time maintaining support for the `_parent` meta field type.
  Remove comma-separated feature parsing for GetIndicesAction
  ...

* master: (80 commits)
  Test: remove faling test that relies on merge order
  Log checkout so SHA is known
  Add link to community Rust Client (elastic#22897)
  "shard started" should show index and shard ID (elastic#25157)
  await fix testWithRandomException
  Change BWC versions on create index response
  Return the index name on a create index response
  Remove incorrect bwc branch logic from master
  Correctly format arrays in output
  [Test] Extending parsing checks for SearchResponse (elastic#25148)
  Scripting: Change keys for inline/stored scripts to source/id (elastic#25127)
  [Test] Add test for custom requests in High Level Rest Client (elastic#25106)
  nested: In case of a single type the _id field should be added to the nested document instead of _uid field.
  `type` and `id` are lost upon serialization of `Translog.Delete`. (elastic#24586)
  fix highlighting docs
  Fix NPE in token_count datatype with null value (elastic#25046)
  Remove the postings highlighter and make unified the default highlighter choice (elastic#25028)
  [Test] Adding test for parsing SearchShardFailure leniently (elastic#25144)
  Fix typo in shards.asciidoc (elastic#25143)
  List Hibernate Search (elastic#25145)
  ...

* master:
  Fix handling of exceptions thrown on HEAD requests
  Fix comment formatting in EvilLoggerTests
  Remove unneeded weak reference from prefix logger