azure: Move most of the bash scripts out of the Azure yamls into separate files

[pietroalbini]

Consider putting any bash script longer than a few lines in a standalone script that can be invoked instead of inlined into yml, perhaps under a /scripts folder.

This allows you to easily run & lint the script, whereas it takes extra steps to do so in yaml.

Originally posted by @zachChilders in #60777

[alexcrichton]

I would personally say that we shouldn't necessarily strive to remove all >1 line scripts from the *.yml files. I think there's a lot to benefit from having it all centralized in one location, especially if there's different scripts for different platforms. If all our CI platforms share the same script I think it's ok to extract, but once Windows does one thing and Unix does another thing I personally find it more clear to follow scripts inline than to have to chase down a bunch of files to make sure everything is synchronized.

[pietroalbini]

This is done.