Improve the Build Process Documentation

[davidfischer]

While working on #4676, I linked from the getting started guides and import guides to the Build Process docs. These docs could use improvement and simplifications

Here's some ideas:

• Detail common errors (out of memory, too much time) and what to do about it. We discuss these issues but we should use the exact verbiage in the error messages in the build output so people can search for them.
• Do we really need a "Writing your own builder" section here? Maybe that should be in the developer docs. Ditto for "Builder responsibility".
• Have details on configuring the right version of Python, right version of MkDocs/Sphinx, and other Yaml config options.
• Do we really need links to tasks.py and doc_builders at the top? These should probably be much further down if anywhere.
• The "You can see the current Docker build images..." paragraph is out of place. It should probably be under "The build environment".

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[humitos]

This issue is still valid and seems to have good ideas to re-work on the docs.

[humitos]

Most of this page was re-written from when this issue was opened. We have troubleshooting sections in other places and examples about how to use the config file, build.jobs and more. I'm closing it.