restructure training and policies and fallback actions docs

[erohmensing]

Proposed changes:

• fixes #1678 master changes (see issue for detailed list of changes)

Probably best to code review by pulling the branch and making the livedocs.

Status (please check what you already did):

• made PR ready for code review
• added some tests for the functionality
• updated the documentation
• updated the changelog

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[JustinaPetr]

Looks great @erohmensing ! The only thing is that in policies page the sizing of the headers are getting a bit confusing. In Fallback Policies section we have a small header for the policy name and then a bigger header for the Configuration which looks like a completely new paragraph (in a way). Can we look into ways to make it a bit easier to follow so that Configuration part would look like it's part of the specific policy paragraph?

[erohmensing]

@JustinaPetr sure, I can do that. It's happening because I decided to bold it instead of making it an actual header (as it is in the Embedding Policy) so that it wouldn't show up in the table of contents as I thought the TOC was perhaps getting a little too fleshed out. I see what you mean though by it looking like a new paragraph because of it being bigger, i'll change it to a header and see what you think.

[erohmensing]

Actually, I just realized the Embedding Policy has everything tabbed in after the configuration, which makes a lot more sense. I'll try that first and see if that's enough to keep the flow