feat(dgeni,docs-utils)!: extract out ToC type

[griest024]

BREAKING CHANGE: the ToC types have been trimmed up to only have fields used

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 new behavior?

• extract ToC into its own type
• remove an unnecessary nesting of ToC data
• remove a lot of unused data from JSON documents

Does this PR introduce a breaking change?

[x] Yes
[ ] No

DaffGuideDoc.tableOfContents has a different type, the json nesting has been removed.

Other information