[DOCS] Adds the 8.3.0 release notes (#134855)

* [DOCS] Adds the 8.3.0 release notes

* Update docs/CHANGELOG.asciidoc

Co-authored-by: Brandon Morelli <bmorelli25@gmail.com>

* Update docs/CHANGELOG.asciidoc

Co-authored-by: Brandon Morelli <bmorelli25@gmail.com>

* Update docs/CHANGELOG.asciidoc

Co-authored-by: Brandon Morelli <bmorelli25@gmail.com>

* Update docs/CHANGELOG.asciidoc

Co-authored-by: Luke Elmers <lukeelmers@gmail.com>

* Review comments

* Updates Content Management enhancement

* Update docs/CHANGELOG.asciidoc

* Update docs/CHANGELOG.asciidoc

* Update docs/CHANGELOG.asciidoc

Co-authored-by: Aleh Zasypkin <aleh.zasypkin@gmail.com>

* Update docs/CHANGELOG.asciidoc

Co-authored-by: Aleh Zasypkin <aleh.zasypkin@gmail.com>

* Update docs/CHANGELOG.asciidoc

Co-authored-by: Aleh Zasypkin <aleh.zasypkin@gmail.com>

* Update docs/CHANGELOG.asciidoc

Co-authored-by: Aleh Zasypkin <aleh.zasypkin@gmail.com>

* Update docs/CHANGELOG.asciidoc

Co-authored-by: Aleh Zasypkin <aleh.zasypkin@gmail.com>

* Update docs/CHANGELOG.asciidoc

Co-authored-by: Aleh Zasypkin <aleh.zasypkin@gmail.com>

* Review comments

* Update docs/CHANGELOG.asciidoc

* Update docs/CHANGELOG.asciidoc

Co-authored-by: Brandon Morelli <bmorelli25@gmail.com>
Co-authored-by: Luke Elmers <lukeelmers@gmail.com>
Co-authored-by: Lisa Cawley <lcawley@elastic.co>
Co-authored-by: Aleh Zasypkin <aleh.zasypkin@gmail.com>
Co-authored-by: gchaps <33642766+gchaps@users.noreply.github.com>