Retire puppet workers

[s0me0ne-unkn0wn]

After worker separation and liberation, puppet workers used for integration tests will not be needed anymore. Their additional functionality (that is only used for those tests) may be integrated into the real workers and gated through #[cfg(test)], as discussed here.

Also, it'd probably open the way for the refactoring of real workers which may be placed into corresponding binary crates in node/core/pvf without the necessity to have separate library and binary crates for every of them.

[mrcnski]

Their additional functionality (that is only used for those tests) may be integrated into the real workers and gated through #[cfg(test)]

Good idea, just keep in mind that #[cfg(test)] may not work across crates. (Maybe can instead use the new test-utils feature.)