Option for host managed memory (#1400)

* Option for host managed memory

* Rename Allocator to MemoryCreator

* Create LinearMemory and MemoryCreator traits in api

* Leave only one as_ptr function in LinearMemory trait

* Memory creator test

* Update comments/docs for LinearMemory and MemoryCreator traits

* Add guard page to the custom memory example

* Remove mut from LinearMemory trait as_ptr

* Host_memory_grow test

crates/jit/src/instantiate.rs

@@ -20,8 +20,8 @@ use wasmtime_environ::{
 };
 use wasmtime_profiling::ProfilingAgent;
 use wasmtime_runtime::{
-    GdbJitImageRegistration, InstanceHandle, InstantiationError, SignatureRegistry,
-    TrapRegistration, VMFunctionBody, VMSharedSignatureIndex, VMTrampoline,
+    GdbJitImageRegistration, InstanceHandle, InstantiationError, RuntimeMemoryCreator,
+    SignatureRegistry, TrapRegistration, VMFunctionBody, VMSharedSignatureIndex, VMTrampoline,
 };
 
 /// An error condition while setting up a wasm instance, be it validation,
@@ -203,6 +203,7 @@ impl CompiledModule {
         is_bulk_memory: bool,
         resolver: &mut dyn Resolver,
         sig_registry: &SignatureRegistry,
+        mem_creator: Option<&dyn RuntimeMemoryCreator>,
     ) -> Result<InstanceHandle, InstantiationError> {
         let data_initializers = self
             .data_initializers
@@ -219,6 +220,7 @@ impl CompiledModule {
             self.finished_functions.clone(),
             self.trampolines.clone(),
             imports,
+            mem_creator,
             &data_initializers,
             self.signatures.clone(),
             self.dbg_jit_registration.as_ref().map(|r| Rc::clone(&r)),
@@ -283,11 +285,13 @@ pub unsafe fn instantiate(
     debug_info: bool,
     is_bulk_memory: bool,
     profiler: &dyn ProfilingAgent,
+    mem_creator: Option<&dyn RuntimeMemoryCreator>,
 ) -> Result<InstanceHandle, SetupError> {
     let instance = CompiledModule::new(compiler, data, debug_info, profiler)?.instantiate(
         is_bulk_memory,
         resolver,
         compiler.signatures(),
+        mem_creator,
     )?;
     Ok(instance)
 }