[main] Update docs for v8.9.1 release (#98416) (#98655)

* Update docs for v8.9.1 release (#98416)

(cherry picked from commit 7985f8ef0f7ed8a001bd74e5fd9ce37222b23865)

* Resolve merge conflicts

---------

Co-authored-by: Volodymyr Krasnikov <129072588+volodk85@users.noreply.github.com>

docs/reference/release-notes.asciidoc

@@ -8,6 +8,7 @@ This section summarizes the changes in each release.
 
 * <<release-notes-8.11.0>>
 * <<release-notes-8.10.0>>
+* <<release-notes-8.9.1>>
 * <<release-notes-8.9.0>>
 * <<release-notes-8.8.2>>
 * <<release-notes-8.8.1>>
@@ -49,6 +50,7 @@ This section summarizes the changes in each release.
 
 include::release-notes/8.11.0.asciidoc[]
 include::release-notes/8.10.0.asciidoc[]
+include::release-notes/8.9.1.asciidoc[]
 include::release-notes/8.9.0.asciidoc[]
 include::release-notes/8.8.2.asciidoc[]
 include::release-notes/8.8.1.asciidoc[]

docs/reference/release-notes/8.9.1.asciidoc

@@ -0,0 +1,53 @@
+[[release-notes-8.9.1]]
+== {es} version 8.9.1
+
+coming[8.9.1]
+
+Also see <<breaking-changes-8.9,Breaking changes in 8.9>>.
+
+[[bug-8.9.1]]
+[float]
+=== Bug fixes
+
+Aggregations::
+* `GlobalAggregator` should call rewrite() before `createWeight()` {es-pull}98091[#98091] (issue: {es-issue}98076[#98076])
+
+Cluster Coordination::
+* Improve exception handling in Coordinator#publish {es-pull}97840[#97840] (issue: {es-issue}97798[#97798])
+
+EQL::
+* Backport fix for async missing events and re-enable the feature {es-pull}98130[#98130]
+
+ILM+SLM::
+* Ignore the `total_shards_per_node` setting on searchable snapshots in frozen {es-pull}97979[#97979]
+* Migrate to data tiers routing configures correct default for mounted indices {es-pull}97936[#97936] (issue: {es-issue}97898[#97898])
+
+Infra/Core::
+* Fix APM trace start time {es-pull}98113[#98113]
+
+Infra/Logging::
+* Add Configuration to `PatternLayout` {es-pull}97679[#97679]
+
+Machine Learning::
+* Fix failure processing Question Answering model output where the input has been spanned over multiple sequences {es-pull}98167[#98167] (issue: {es-issue}97917[#97917])
+
+Search::
+* `UnmappedFieldFetcher` should ignore nested fields {es-pull}97987[#97987] (issue: {es-issue}97684[#97684])
+
+[[enhancement-8.9.1]]
+[float]
+=== Enhancements
+
+Authentication::
+* Upgrade xmlsec to 2.1.8 {es-pull}97741[#97741]
+
+Infra/Core::
+* Enhance regex performance with duplicate wildcards {es-pull}98176[#98176]
+
+Machine Learning::
+* Add setting to scale the processor count used in the model assignment planner {es-pull}98296[#98296]
+
+Search::
+* Refactor nested field handling in `FieldFetcher` {es-pull}97683[#97683]
+
+