separate binaries feature was refactored

[kogeler]

The current implementation of separate binaries has some disadvantages:

• previously added separate binary options have hidden logic. For example, they affect behavior of existing variables. node_binary variable has to contain a root HTTP path or link to a file depending of other variables
• we can't use different roots for the binary HTTP links
• we can't use arbitrary file names in binary HTTP links
• we can't deploy more than one node on one instances because worker binary files will overwrite each other

These changes make the separate binary configurate flatter (without lists) and clear. I don't think that we will have tens of separate worker binaries in the future.

[PierreBesson]

I'm not sure how these changes would behave for a variety of nodes. Could you check its compatibility with at least polkadot/cumulus.