Remove global state for trap registration (#909)

* Remove global state for trap registration

There's a number of changes brought about in this commit, motivated by a
few things. One motivation was to remove an instance of using
`lazy_static!` in an effort to remove global state and encapsulate it
wherever possible. A second motivation came when investigating a
slowly-compiling wasm module (a bit too slowly) where a good chunk of
time was spent in managing trap registrations.

The specific change made here is that `TrapRegistry` is now stored
inside of a `Compiler` instead of inside a global. Additionally traps
are "bulk registered" for a module rather than one-by-one. This form of
bulk-registration allows optimizing the locks used here, where a lock is
only held for a module at-a-time instead of once-per-function.

With these changes the "unregister" logic has also been tweaked a bit
here and there to continue to work. As a nice side effect the `Compiler`
type now has one fewer field that requires actual mutability and has
been updated for multi-threaded compilation, nudging us closer to a
world where we can support multi-threaded compilation. Yay!

In terms of performance improvements, a local wasm test file that
previously took 3 seconds to compile is now 10% faster to compile,
taking ~2.7 seconds now.

* Perform trap resolution after unwinding

This avoids taking locks in signal handlers which feels a bit iffy...

* Remove `TrapRegistration::dummy()`

Avoid an case where you're trying to lookup trap information from a
dummy module for something that happened in a different module.

* Tweak some comments

crates/api/src/trampoline/mod.rs

@@ -43,24 +43,27 @@ pub unsafe fn generate_raw_func_export(
 }
 
 pub fn generate_global_export(
+    store: &Store,
     gt: &GlobalType,
     val: Val,
 ) -> Result<(wasmtime_runtime::Export, GlobalState)> {
-    create_global(gt, val)
+    create_global(store, gt, val)
 }
 
 pub fn generate_memory_export(
+    store: &Store,
     m: &MemoryType,
 ) -> Result<(wasmtime_runtime::InstanceHandle, wasmtime_runtime::Export)> {
-    let instance = create_handle_with_memory(m)?;
+    let instance = create_handle_with_memory(store, m)?;
     let export = instance.lookup("memory").expect("memory export");
     Ok((instance, export))
 }
 
 pub fn generate_table_export(
+    store: &Store,
     t: &TableType,
 ) -> Result<(wasmtime_runtime::InstanceHandle, wasmtime_runtime::Export)> {
-    let instance = create_handle_with_table(t)?;
+    let instance = create_handle_with_table(store, t)?;
     let export = instance.lookup("table").expect("table export");
     Ok((instance, export))
 }