It is required in order to work correctly with bulk scorer implementations
that change the scorer during the collection process. Otherwise sub collectors
might call `Scorer.score()` on the wrong scorer.

Closes #27131

* master:
  Enhances exists queries to reduce need for `_field_names` (elastic#26930)
  Added new terms_set query
  Set request body to required to reflect the code base (elastic#27188)
  Update Docker docs for 6.0.0-rc2 (elastic#27166)
  Add version 6.0.0
  Docs: restore now fails if it encounters incompatible settings (elastic#26933)
  Convert index blocks to cluster block exceptions (elastic#27050)
  [DOCS] Link remote info API in Cross Cluster Search docs page
  Fix Laplace scorer to multiply by alpha (and not add) (elastic#27125)
  [DOCS] Clarify migrate guide and search request validation
  Raise IllegalArgumentException if query validation failed (elastic#26811)
  prevent duplicate fields when mixing parent and root nested includes (elastic#27072)
  TopHitsAggregator must propagate calls to `setScorer`. (elastic#27138)

* master:
  Remove checkpoint tracker bit sets setting
  Fix stable BWC branch detection logic
  Fix logic detecting unreleased versions
  Enhances exists queries to reduce need for `_field_names` (elastic#26930)
  Added new terms_set query
  Set request body to required to reflect the code base (elastic#27188)
  Update Docker docs for 6.0.0-rc2 (elastic#27166)
  Add version 6.0.0
  Docs: restore now fails if it encounters incompatible settings (elastic#26933)
  Convert index blocks to cluster block exceptions (elastic#27050)
  [DOCS] Link remote info API in Cross Cluster Search docs page
  Fix Laplace scorer to multiply by alpha (and not add) (elastic#27125)
  [DOCS] Clarify migrate guide and search request validation
  Raise IllegalArgumentException if query validation failed (elastic#26811)
  prevent duplicate fields when mixing parent and root nested includes (elastic#27072)
  TopHitsAggregator must propagate calls to `setScorer`. (elastic#27138)

* master:
  Lazy initialize checkpoint tracker bit sets
  Remove checkpoint tracker bit sets setting
  Fix stable BWC branch detection logic
  Fix logic detecting unreleased versions
  Enhances exists queries to reduce need for `_field_names` (#26930)
  Added new terms_set query
  Set request body to required to reflect the code base (#27188)
  Update Docker docs for 6.0.0-rc2 (#27166)
  Add version 6.0.0
  Docs: restore now fails if it encounters incompatible settings (#26933)
  Convert index blocks to cluster block exceptions (#27050)
  [DOCS] Link remote info API in Cross Cluster Search docs page
  Fix Laplace scorer to multiply by alpha (and not add) (#27125)
  [DOCS] Clarify migrate guide and search request validation
  Raise IllegalArgumentException if query validation failed (#26811)
  prevent duplicate fields when mixing parent and root nested includes (#27072)
  TopHitsAggregator must propagate calls to `setScorer`. (#27138)

* 6.x:
  Lazy initialize checkpoint tracker bit sets
  Remove checkpoint tracker bit sets setting
  Tests: Fix FullClusterRestartIT.testSnapshotRestore test failing in 6.x (#27218)
  Fix FullClusterRestartIT using lenient booleans with 6.0
  Fix stable BWC branch detection logic
  Add version 6.0.0
  Fix logic detecting unreleased versions
  Skips exists query tests on unsupported versions
  Enhances exists queries to reduce need for `_field_names` (#26930)
  Added new terms_set query
  Set request body to required to reflect the code base (#27188)
  Update Docker docs for 6.0.0-rc2 (#27166)
  Docs: restore now fails if it encounters incompatible settings (#26933)
  Convert index blocks to cluster block exceptions (#27050)
  [DOCS] Link remote info API in Cross Cluster Search docs page
  prevent duplicate fields when mixing parent and root nested includes (#27072)
  TopHitsAggregator must propagate calls to `setScorer`. (#27138)