Build Polkadot Nodes in CI - fixes artifact generation (#1410)

* new workflow and adjust node builder

* fix examples by fixing artifacts script

* use-nodes instead of use-substrate

* update yamls

* build polkadot

* remove the on-push trigger again, now that polkadot built in the CI

* add default implementation again

testing/substrate-runner/src/lib.rs

@@ -21,7 +21,7 @@ pub struct SubstrateNodeBuilder {
 
 impl Default for SubstrateNodeBuilder {
     fn default() -> Self {
-        Self::new()
+        SubstrateNodeBuilder::new()
     }
 }
 
@@ -29,11 +29,23 @@ impl SubstrateNodeBuilder {
     /// Configure a new Substrate node.
     pub fn new() -> Self {
         SubstrateNodeBuilder {
-            binary_paths: vec!["substrate-node".into(), "substrate".into()],
+            binary_paths: vec![],
             custom_flags: Default::default(),
         }
     }
 
+    /// Provide "substrate-node" and "substrate" as binary paths
+    pub fn substrate(&mut self) -> &mut Self {
+        self.binary_paths = vec!["substrate-node".into(), "substrate".into()];
+        self
+    }
+
+    /// Provide "polkadot" as binary path.
+    pub fn polkadot(&mut self) -> &mut Self {
+        self.binary_paths = vec!["polkadot".into()];
+        self
+    }
+
     /// Set the path to the `substrate` binary; defaults to "substrate-node"
     /// or "substrate".
     pub fn binary_paths<Paths, S>(&mut self, paths: Paths) -> &mut Self