Template: Allow rolling restart for restart change_mode

[Oloremo]

Proposal

Currently, template stanza won't trigger an update stanza if the template needs to be updated, which will lead to an unexpected downtime in some cases.

It was initially requested here: #2202
But that issue was closed, not sure why. I think it should remain open as a feature request unless Hashicorp is against implementing it.

4 years have passed - any changes that will be implemented?

[tino]

Let's concentrate the discussion here: #6151

[tgross]

Going to close this in lieu of #6151

[github-actions]

I'm going to lock this issue because it has been closed for 120 days ⏳. This helps our maintainers find and focus on the active issues.
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