Redefine structure for release notes section

[patiencedaur]

Resolves #2734

[xuniq]

Looks good to me.

[art-dr]

I would say the structure is good.

The only thing that bothers me is that in this menu you can see the "Summary" chapter somewhere between other chapters listed. Yet when you open the first link, which is "Release policies", the very first heading is also "Summary", but it's another summary of another chapter. It got me a bit confused.

[veod32]

The new structure is good!
A few comments:

The only thing that bothers me is that in this menu you can see the "Summary" chapter somewhere between other chapters listed. Yet when you open the first link, which is "Release policies", the very first heading is also "Summary", but it's another summary of another chapter. It got me a bit confused.

1. Agree with @arctic-dreamer 's comment above. I would remove the Summary title on this page and the corresponding ToC item here.

2. On the Release policies main page, detailed ToC also seems redundant. Links to both the new release policy and the legacy one are obvious from the summary text.

3. Release notes main page ToC:
   I would rename the Versions item and the title on the corresponding page to something like Release notes on Tarantool versions.
   Otherwise, when you look at the current ToC, it's hard to guess where the main thing is—the release notes themselves.

[patiencedaur]

@arctic-dreamer, @veod32, thank you for your suggestions! Does it look good now?