Script worker

Add a new worker called "script", which compiles previously introduced
parser using LLVM into bytecode for execution. It also provides a set of
functionality available at runtime for such scripts.

Note that it's a breaking change in terms of the interface. If before
the workload configuration was passed as a first positional argument,
now it has to be passed via `-c workload.toml`, to distinguish from
passing a script via `-f script.ber`.

Author: erthalion

Cargo.lock

@@ -28,3 +28,6 @@ io-uring = "0.7.10"
 enum_dispatch = "0.3.13"
 pest = "2.8.1"
 pest_derive = "2.8.1"
+llvm-sys = "201.0.1"
+docopt = "1.1.1"
+signal-hook = "0.3.18"