bench-api: configure execution with a flags string (#4096)

As discussed previously, we need a way to be able to configure Wasmtime when running it in the Sightglass benchmark infrastructure. The easiest way to do this seemed to be to pass a string from Sightglass to the `bench-api` library and parse this in the same way that Wasmtime parses its CLI flags. The structure that contains these flags is `CommonOptions`, so it has been moved to its own crate to be depended on by both `wasmtime-cli` and `wasmtime-bench-api`. Also, this change adds an externally-visible function for parsing a string into `CommonOptions`, which is used for configuring an engine.

deny.toml

@@ -40,4 +40,9 @@ skip-tree = [
     # This is somewhat unmaintained at this point and seems to pull in an old
     # version of `env_logger`, so ignore it.
     { name = "pretty_env_logger", depth = 20 },
+
+    # This crate depends on an old version of the `uuid` crate: `wasmtime-cli ->
+    # listenfd -> uuid`. Once `listenfd` upgrades to `uuid` v1.0.0, this can be
+    # removed.
+    { name = "listenfd", depth = 20 },
 ]