feat(dgeni,daffio): consolidate docs list rendering and generation

[griest024]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/graycoreio/daffodil/blob/develop/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[x] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

The API and guides docsgen and rendering are very similar and duplicated

What is the new behavior?

The API and guides have a DRY docsgen and rendering

• the nav list generation in dgeni has been combined into a single processor with a configured transform
• the guides and API nav lists now have a unified type for wider compatiblity
• the path configurators are now unified between API and guides
• the docs service is no longer responsible for fetching nav lists and this is now handled by an index service
• the guides and API lsit components have been combined

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information