[backport 3.3] tools: update release notes template

[TarantoolBot]

(This PR is a backport of #11210 to release/3.3 to a future 3.3.2 release.)

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The given template comes from the time, when we had 1.10 and 2.x with the old release policy (see https://github.com/orgs/tarantool/discussions/6182). In fact, almost every aspect of this template is obsolete now.

For example, we have no stable and non-stable releases anymore: there are pre-releases (marked with alpha, beta, rc keywords) and releases. We don't need to say explicitly that the given release is stable.

Also, 1.10 is not LTS anymore (it is EOL) and 2.11 is not the latest series.

The links needs an update too.

So, I decided to write these templates from scratch, but keep the idea: give some release status information, highlight notable changes (for feature releases), provide a few hints about the update procedure.

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Resulting templates are below.

3.x

# Overview

Tarantool 3.x is the recommended release series. Users of Tarantool 2.11 are
encouraged to update to the latest 3.x release.

This release introduces {{FEATURES}} improvements and resolves {{BUGFIXES}}
bugs since **TBD**.

Notable changes are:

* **TBD**
* **TBD**
* **TBD**

Please, consider the full list of user-visible changes below.

## Compatibility

Tarantool 2.x and 3.x are compatible in the binary data layout, client-server
protocol, and replication protocol. It means that the updating may be performed
with zero downtime for read requests and the-order-of-network-lag downtime for
write requests.

Please, follow the [upgrade procedure][upgrade] to plan your update actions.

Users of Tarantool 2.x may be interested in the [compat][compat] options that
allow to imitate some 2.x behavior. This allows to perform application code
update step-by-step, not all-at-once.

[compat]: https://www.tarantool.io/en/doc/latest/reference/configuration/configuration_reference/#compat

[upgrade]: https://www.tarantool.io/en/doc/latest/book/admin/upgrades/

2.11

# Overview

2.x is the old stable release series. Users are encouraged to update to the
latest 3.x release.

This is a bugfix release. It resolves {{BUGFIXES}} issues since the previous
version.

Please, consider the full list of user-visible changes below.

## Compatibility

Tarantool 2.x and 3.x are compatible in the binary data layout, client-server
protocol, and replication protocol. It means that the updating may be performed
with zero downtime for read requests and the-order-of-network-lag downtime for
write requests.

Please, follow the [upgrade procedure][upgrade] to plan your update actions.

[upgrade]: https://www.tarantool.io/en/doc/latest/book/admin/upgrades/

[coveralls]

coverage: 87.457% (-0.01%) from 87.467%
when pulling 6f9e4e4 on backport/release/3.3/11210
into 59fe8bd
on release/3.3.