Add release notes on version 3.0.0.0-alpha1 (#3414)

Author: noCharger

release-notes/opensearch-sql.release-notes-3.0.0.0-alpha1.md

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+Compatible with OpenSearch and OpenSearch Dashboards Version 3.0.0.0-alpha1
+
+### Breaking Changes
+
+* [Release 3.0] Bump gradle 8.10.2 / JDK23 / 3.0.0.0-alpha1 on SQL plugin ([#3319](https://github.com/opensearch-project/sql/pull/3319))
+* [v3.0.0] Remove SparkSQL support ([#3306](https://github.com/opensearch-project/sql/pull/3306))
+* [v3.0.0] Remove opendistro settings and endpoints ([#3326](https://github.com/opensearch-project/sql/pull/3326))
+* [v3.0.0] Deprecate SQL Delete statement ([#3337](https://github.com/opensearch-project/sql/pull/3337))
+* [v3.0.0] Deprecate scroll API usage ([#3346](https://github.com/opensearch-project/sql/pull/3346))
+* [v3.0.0] Deprecate OpenSearch DSL format ([#3367](https://github.com/opensearch-project/sql/pull/3367))
+
+### Features
+
+* PPL: Add `json` function and `cast(x as json)` function ([#3243](https://github.com/opensearch-project/sql/pull/3243))
+
+### Enhancements
+
+* Add other functions to SQL query validator ([#3304](https://github.com/opensearch-project/sql/pull/3304))
+* Improved patterns command with new algorithm ([#3263](https://github.com/opensearch-project/sql/pull/3263))
+* Clean up syntax error reporting ([#3278](https://github.com/opensearch-project/sql/pull/3278))
+
+### Maintenance
+
+* Build: Centralise dependencies version - Pt1 ([#3294](https://github.com/opensearch-project/sql/pull/3294))
+* Remove dependency from async-query-core to datasources ([#2891](https://github.com/opensearch-project/sql/pull/2891))