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.

src/commands/wast.rs

@@ -1,10 +1,10 @@
 //! The module that implements the `wasmtime wast` command.
 
-use crate::CommonOptions;
 use anyhow::{Context as _, Result};
 use clap::Parser;
 use std::path::PathBuf;
 use wasmtime::{Engine, Store};
+use wasmtime_cli_flags::CommonOptions;
 use wasmtime_wast::WastContext;
 
 lazy_static::lazy_static! {