[RF-DOCS] Review Action View Overview Guide (rails#51435)

Review and improve Action View Overview guide [ci-skip]

* Add more code examples and update existing examples.
* Consolidate all topics related to partials in this guide.
* Restructure sections for better flow and readability.
* Reword the introduction and clarify how Action View fits in.

Note: This guide has content that's intertwined with the Layouts and Rendering guide,
with some duplicate content and overlapping concepts. A follow-on PR will focus on
the other guide and then we will do a pass over both guides together.

Co-authored-by: Carlos Antonio da Silva <[email protected]>

Author: bhumi1102