[C++][Docs] Re-Organize the Existing Acero Streaming Engine Documentation

The current document is too-length. By creating sub-pages for each example and explain the code and provide a better description, that would be much better in terms of readability and browsing the content. The idea is to create a sub-folder in the examples called 'acero` and include each example in a separate `.cc` file. This is the code change. Following this, the documentation page on the website can be splitted into sub-pages. This is the only change suggested for this sub-task. 

There is already a JIRA: https://github.com/apache/arrow/issues/20284 to improve the internal content. So it would be used for re-writing the contnet. 

**Reporter**: [Vibhatha Lakmal Abeykoon](https://issues.apache.org/jira/browse/ARROW-17177) / @vibhatha
**Assignee**: [Vibhatha Lakmal Abeykoon](https://issues.apache.org/jira/browse/ARROW-17177) / @vibhatha
#### Related issues:
- [[C++][Documentation] Update overview of Arrow components/layers](https://github.com/apache/arrow/issues/30267) (relates to)
- [[Docs] Improve Acero Documentation](https://github.com/apache/arrow/issues/20284) (relates to)
#### PRs and other links:
- [GitHub Pull Request #13713](https://github.com/apache/arrow/pull/13713)
- [GitHub Pull Request #14185](https://github.com/apache/arrow/pull/14185)

_{**Note**: *This issue was originally created as [ARROW-17177](https://issues.apache.org/jira/browse/ARROW-17177). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}

Start by locating the current Acero documentation page and its examples directory. Review how the existing examples are organized, then separate each example into its own .cc file under an acero sub-folder and split the website documentation into corresponding sub-pages; completion means the examples and pages are reorganized without the broader content rewrite covered by issue 20284.

Written by the indexing model from the issue text.