Improve documentation of Istio version

[triffer]

Description

We should provide a better documentation about what Istio version will be installed by a specific release. We can do that by extending the release notes with the information about the bundled Istio version. Additionally, we should document how users can get the Envoy version of this Istio version.

Reasons Better documentation about Istio version provided by module.

AC

• [x] Release-notes generation in pipeline adds Istio and Envoy version during release
• [x] Istio module documentation is updated during istiop bump task to include the Istio and envoy version

DoD:

• [x] Provide documentation.

Attachments

• Release created with version automation in fork repository
• https://github.com/kyma-project/istio/pull/847

[strekm]

• extend release notes generation to include Istio and Envoy version
• extend Istio main documentation during Istio bump (consider automation)

[triffer]

I checked the automation for updating the main README.md, but I think it's not worth the effort.