Add setting to relax SA1519 to allow consecutive with braces omitted on all but the last one

#2180 modified the rule to disallow this:

using (var a = GetDisposable())
using (var b = GetAnotherDisposable())
{
}

This was permitted in classic StyleCop. It would be helpful to have a setting that allows this behaviour to be retained.

[appel1]

I’d prefer if the classic StyleCop behavior was the default with a setting to make it more strict if wanted/needed.

[sharwell]

📝 We made the default compatible with StyleCop Classic so no updates to KnownChanges.md were required.