wasmtime: Refactor how imports are resolved (#2102)

This commit removes all import resolution handling from the
`wasmtime-jit` crate, instead moving the logic to the `wasmtime` crate.
Previously `wasmtime-jit` had a generic `Resolver` trait and would do
all the import type matching itself, but with the upcoming
module-linking implementation this is going to get much trickier.

The goal of this commit is to centralize all meaty "preparation" logic
for instantiation into one location, probably the `wasmtime` crate
itself. Instantiation will soon involve recursive instantiation and
management of alias definitions as well. Having everything in one
location, especially with access to `Store` so we can persist
instances for safety, will be quite convenient.

Additionally the `Resolver` trait isn't really necessary any more since
imports are, at the lowest level, provided as a list rather than a map
of some kind. More generic resolution functionality is provided via
`Linker` or user layers on top of `Instance::new` itself. This makes
matching up provided items to expected imports much easier as well.

Overall this is largely just moving code around, but most of the code
in the previous `resolve_imports` phase can be deleted since a lot of it
is handled by surrounding pieces of `wasmtime` as well.

crates/jit/src/instantiate.rs

@@ -5,10 +5,8 @@
 
 use crate::code_memory::CodeMemory;
 use crate::compiler::{Compilation, Compiler};
-use crate::imports::resolve_imports;
 use crate::link::link_module;
 use crate::object::ObjectUnwindInfo;
-use crate::resolver::Resolver;
 use object::File as ObjectFile;
 use serde::{Deserialize, Serialize};
 use std::any::Any;
@@ -24,10 +22,10 @@ use wasmtime_environ::{
     ModuleEnvironment, ModuleTranslation, StackMapInformation, TrapInformation,
 };
 use wasmtime_profiling::ProfilingAgent;
-use wasmtime_runtime::VMInterrupts;
 use wasmtime_runtime::{
-    GdbJitImageRegistration, InstanceHandle, InstantiationError, RuntimeMemoryCreator,
-    SignatureRegistry, StackMapRegistry, VMExternRefActivationsTable, VMFunctionBody, VMTrampoline,
+    GdbJitImageRegistration, Imports, InstanceHandle, InstantiationError, RuntimeMemoryCreator,
+    SignatureRegistry, StackMapRegistry, VMExternRefActivationsTable, VMFunctionBody, VMInterrupts,
+    VMTrampoline,
 };
 
 /// An error condition while setting up a wasm instance, be it validation,
@@ -245,7 +243,7 @@ impl CompiledModule {
     /// See `InstanceHandle::new`
     pub unsafe fn instantiate(
         &self,
-        resolver: &mut dyn Resolver,
+        imports: Imports<'_>,
         signature_registry: &mut SignatureRegistry,
         mem_creator: Option<&dyn RuntimeMemoryCreator>,
         interrupts: Arc<VMInterrupts>,
@@ -271,7 +269,6 @@ impl CompiledModule {
 
         let finished_functions = self.finished_functions.0.clone();
 
-        let imports = resolve_imports(&self.module, signature_registry, resolver)?;
         InstanceHandle::new(
             self.module.clone(),
             self.code.clone(),