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.

crates/cli-flags/Cargo.toml

@@ -0,0 +1,28 @@
+[package]
+name = "wasmtime-cli-flags"
+version = "0.37.0"
+authors = ["The Wasmtime Project Developers"]
+description = "Exposes common CLI flags used for running Wasmtime"
+license = "Apache-2.0 WITH LLVM-exception"
+repository = "https://github.com/bytecodealliance/wasmtime"
+documentation = "https://docs.rs/wasmtime-cache/"
+edition = "2021"
+
+[dependencies]
+anyhow = "1.0.19"
+clap = { version = "3.1.12", features = ["color", "suggestions", "derive"] }
+file-per-thread-logger = "0.1.1"
+pretty_env_logger = "0.4.0"
+rayon = "1.5.0"
+wasmtime = { path = "../wasmtime", version = "0.37.0", default-features = false }
+
+[features]
+default = [
+    "wasmtime/cache",
+    "wasmtime/cranelift",
+    "wasmtime/jitdump",
+    "wasmtime/vtune",
+]
+pooling-allocator = []
+memory-init-cow = []
+wasm-backtrace = []