[3pt] Publish Tarantool testing matrix

[kyukhin]

It might be useful if user can verify which OSes and which version are being tested regularily.
Let's publish our testing matrix.

[artur-barsegyan]

I suggest posting in the documentation.

If we write that this is tested only on certain versions of operating systems on the Download page it may scare the user away from trying the product.

This information is for production and it is better to write about it in the documentation. But we can place a link to that information page on the Download page.

[NickVolynkin]

Just discussed this with @artur-barsegyan, @Totktonada and @artembo, agreed on the following:

• We make a new Testing Matrix page page in the documentation for this matrix: issue [5pt] Contents and place for the Testing Matrix page #1752
• The page contents should be autogenerated from .gitlab-ci.yml or .github/workflows/main.yml into a list-table in reStructuredText.
• On the Downloads page we'll add a link to the new Testing Matrix page below the main content on each tab.

[NickVolynkin]

https://github.com/tarantool/tarantool/tree/master/.github/workflows

[veod32]

Just discussed this with @artur-barsegyan, @Totktonada and @artembo, agreed on the following:

• We make a new Testing Matrix page in the documentation for this matrix: issue [5pt] Contents and place for the Testing Matrix page #1752
• The page contents should be autogenerated from .gitlab-ci.yml or .github/workflows/main.yml into a list-table in reStructuredText.
• On the Downloads page, we'll add a link to the new Testing Matrix page below the main content on each tab.

While processing the Q4 2020 Release Notes (2.7.1, 2.6.2, 2.5.3, 1.10.9) according to the #1916, I found these two RN items:

• Deploy packages for Fedora 32 ( replication.reconnect_timeout option #4966).
• Deploy packages for Debian Bullseye (gh-5638).

I think they bring some extra ToDos to this Testing Matrix ticket:

• Verify the list of the supported OS's in https://github.com/tarantool/tarantool/tree/master/.github/workflows. For example, I see Fedora 32 there but don't see Debian Bullseye.
• Make the Download page consistent in terms of mentioning the supported OS's. Currently, we have the list of supported versions only for Fedora and not for other operating systems.

[Totktonada]

Verify the list of the supported OS's in https://github.com/tarantool/tarantool/tree/master/.github/workflows. For example, I see Fedora 32 there but don't see Debian Bullseye.

It was added in tarantool/tarantool@e0a33ff