Retire puppet workers (#1449)

Closes #583

After the separation of PVF worker binaries, dedicated puppet workers
are not needed for tests anymore. The production workers can be used
instead, avoiding some code duplication and decreasing complexity.

The changes also make it possible to further refactor the code to
isolate workers completely.

polkadot/node/core/pvf/common/src/worker/mod.rs

@@ -60,6 +60,10 @@ macro_rules! decl_worker_main {
 					println!("{}", $worker_version);
 					return
 				},
+				"test-sleep" => {
+					std::thread::sleep(std::time::Duration::from_secs(5));
+					return
+				},
 				subcommand => {
 					// Must be passed for compatibility with the single-binary test workers.
 					if subcommand != $expected_command {