Add ability to advice replacing usually outdated *-latest runners with specific ones #564
Description
In the last decade, most of the time *-latest github runners did not point to the latest operating system as most of the time there were already newer ones available, as preview. That is due to Github policy of being very conservative with runners switch.
The main problem with this is that is gives users the false impression that they are using a recent operating system. As of today these labels point to 2-3 years old Ubuntu and Windows.
The secondary problem is that user have no control when migration to new runners happens and usually this happens gradually in a 2-3 months interval, sometimes even having subsequent jobs alternating between different runners.
Due to this, actionlint could warn the users to use specific versions, as this will make their executions predictable and reproducible.
As new OS versions are introduced only 2-3 years, we could also add another warning about outdated runners, like ubuntu-20.04, but for this one user should be able to ignore it, as sometimes they cannot make the switch right away.