Remove all global state from the caching system (#863)

* Remove all global state from the caching system

This commit is a continuation of an effort to remove usages of
`lazy_static!` and similar global state macros which can otherwise be
accomodated with passing objects around. Previously there was a global
cache system initialized per-process, but it was initialized in a bit of
a roundabout way and wasn't actually reachable from the `wasmtime` crate
itself. The changes here remove all global state, refactor many of the
internals in the cache system, and makes configuration possible through
the `wasmtime` crate.

Specifically some changes here are:

* Usage of `lazy_static!` and many `static` items in the cache module
  have all been removed.
* Global `cache_config()`, `worker()`, and `init()` functions have all
  been removed. Instead a `CacheConfig` is a "root object" which
  internally owns its worker and passing around the `CacheConfig` is
  required for cache usage.
* The `wasmtime::Config` structure has grown options to load and parse
  cache files at runtime. Currently only loading files is supported,
  although we can likely eventually support programmatically configuring
  APIs as well.
* Usage of the `spin` crate has been removed and the dependency is removed.
* The internal `errors` field of `CacheConfig` is removed, instead
  changing all relevant methods to return a `Result<()>` instead of
  storing errors internally.
* Tests have all been updated with the new interfaces and APIs.

Functionally no real change is intended here. Usage of the `wasmtime`
CLI, for example, should still enable the cache by default.

* Fix lightbeam compilation

src/commands/wast.rs

@@ -1,11 +1,10 @@
 //! The module that implements the `wasmtime wast` command.
 
 use crate::{init_file_per_thread_logger, pick_compilation_strategy, CommonOptions};
-use anyhow::{bail, Context as _, Result};
-use std::{fmt::Write, path::PathBuf};
+use anyhow::{Context as _, Result};
+use std::path::PathBuf;
 use structopt::{clap::AppSettings, StructOpt};
 use wasmtime::{Config, Engine, Store};
-use wasmtime_environ::cache_init;
 use wasmtime_wast::WastContext;
 
 /// Runs a WebAssembly test script file
@@ -27,28 +26,11 @@ pub struct WastCommand {
 impl WastCommand {
     /// Executes the command.
     pub fn execute(&self) -> Result<()> {
-        let log_config = if self.common.debug {
+        if self.common.debug {
             pretty_env_logger::init();
-            None
         } else {
             let prefix = "wast.dbg.";
             init_file_per_thread_logger(prefix);
-            Some(prefix)
-        };
-
-        let errors = cache_init(
-            !self.common.disable_cache,
-            self.common.config.as_ref(),
-            log_config,
-        );
-
-        if !errors.is_empty() {
-            let mut message = String::new();
-            writeln!(message, "Cache initialization failed. Errors:")?;
-            for e in errors {
-                writeln!(message, "  -> {}", e)?;
-            }
-            bail!(message);
         }
 
         let mut config = Config::new();
@@ -60,6 +42,7 @@ impl WastCommand {
                 self.common.cranelift,
                 self.common.lightbeam,
             )?)?;
+        self.common.configure_cache(&mut config)?;
 
         if self.common.optimize {
             config.cranelift_opt_level(wasmtime::OptLevel::Speed);