[Docs] Clarify processes for first-time contributors

Per [this discussion](https://lists.apache.org/thread/hycr4ghh7csspvm9jyffvqh8qo5koobg), improvements should be considered to reduce friction for first-time contributors through documentation of environment setup, CI checks, code review expectations, etc. Some of this exists scattered in various locations throughout documentation (e.g., language-specific development environments are documented), but it can be difficult to find. The [contributing page](https://arrow.apache.org/docs/developers/contributing.html) has some pointers at the bottom.

**Reporter**: [Todd Farmer](https://issues.apache.org/jira/browse/ARROW-17447) / @toddfarmer

_{**Note**: *This issue was originally created as [ARROW-17447](https://issues.apache.org/jira/browse/ARROW-17447). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}

Start with docs/developers/contributing.html and the linked discussion, then locate the scattered language-specific development-environment guidance and existing CI and review documentation. Done means first-time contributors can find consolidated, clear instructions for environment setup, CI checks, and code review expectations from the contributing page.

Written by the indexing model from the issue text.