Add release notes for v8.18.0 release (#126735)

* Update docs for v8.18.0 release

* Update docs/reference/release-notes/highlights.asciidoc

* Don't lose nice edits, just add net new stuff

* revert highlights to edited version

---------

Co-authored-by: Liam Thompson <[email protected]>

Author: elasticsearchmachine

docs/reference/release-notes/8.18.0.asciidoc

@@ -29,6 +29,9 @@ Analysis::
 * Adjust exception thrown when unable to load hunspell dict {es-pull}123743[#123743]
 * Non existing synonyms sets do not fail shard recovery for indices {es-pull}125659[#125659] (issue: {es-issue}125603[#125603])
 
+Authentication::
+* Fix NPE for missing Content Type header in OIDC Authenticator {es-pull}126191[#126191]
+
 CAT APIs::
 * Fix cat_component_templates documentation {es-pull}120487[#120487]
 
@@ -62,6 +65,7 @@ ES|QL::
 * Fix attribute set equals {es-pull}118823[#118823]
 * Fix double lookup failure on {esql} {es-pull}115616[#115616] (issue: {es-issue}111398[#111398])
 * Fix queries with document level security on lookup indexes {es-pull}120617[#120617] (issue: {es-issue}120509[#120509])
+* Fix usage of already released null block in `ValueSourceReaderOperator` {es-pull}126411[#126411] (issue: {es-issue}125850[#125850])
 * Fix writing for LOOKUP status {es-pull}119296[#119296] (issue: {es-issue}119086[#119086])
 * Implicit numeric casting for CASE/GREATEST/LEAST {es-pull}122601[#122601] (issue: {es-issue}121890[#121890])
 * Lazy collection copying during node transform {es-pull}124424[#124424]
@@ -142,6 +146,7 @@ Search::
 * Handle search timeout in `SuggestPhase` {es-pull}122357[#122357] (issue: {es-issue}122186[#122186])
 * In this pr, a 400 error is returned when _source / _seq_no / _feature / _nested_path / _field_names is requested, rather a 5xx {es-pull}117229[#117229]
 * Load `FieldInfos` from store if not yet initialised through a refresh on `IndexShard` {es-pull}125650[#125650] (issue: {es-issue}125483[#125483])
+* Log stack traces on data nodes before they are cleared for transport {es-pull}125732[#125732]
 * Re-enable parallel collection for field sorted top hits {es-pull}125916[#125916]
 * Skip fetching _inference_fields field in legacy semantic_text format {es-pull}121720[#121720]
 * Support indices created in ESv6 and updated in ESV7 using different LuceneCodecs as archive in current version. {es-pull}125389[#125389]
@@ -157,6 +162,10 @@ Snapshot/Restore::
 Suggesters::
 * Return an empty suggestion when suggest phase times out {es-pull}122575[#122575] (issue: {es-issue}122548[#122548])
 
+
+TLS::
+* Set `keyUsage` for generated HTTP certificates and self-signed CA {es-pull}126376[#126376] (issue: {es-issue}117769[#117769])
+
 Transform::
 * If the Transform is configured to write to an alias as its destination index, when the delete_dest_index parameter is set to true, then the Delete API will now delete the write index backing the alias {es-pull}122074[#122074] (issue: {es-issue}121913[#121913])
 
@@ -450,4 +459,3 @@ Search::
 Watcher::
 * Script for migrating `.watches` and `.triggered_watches` indices {es-pull}120371[#120371]
 
-

docs/reference/release-notes/highlights.asciidoc

@@ -63,4 +63,3 @@ LOOKUP JOIN combines data from your {esql} queries with matching records from a
 
 // end::notable-highlights[]
 
-