Tidy up some internals of instance allocation (#5346)

* Simplify the `ModuleRuntimeInfo` trait slightly

Fold two functions into one as they're only called from one location
anyway.

* Remove ModuleRuntimeInfo::signature

This is redundant as the array mapping is already stored within the
`VMContext` so that can be consulted rather than having a separate trait
function for it. This required altering the `Global` creation slightly
to work correctly in this situation.

* Remove a now-dead constant

* Shared `VMOffsets` across instances

This commit removes the computation of `VMOffsets` to being per-module
instead of per-instance. The `VMOffsets` structure is also quite large
so this shaves off 112 bytes per instance which isn't a huge impact but
should help lower the cost of instantiating small modules.

* Remove `InstanceAllocator::adjust_tunables`

This is no longer needed or necessary with the pooling allocator.

* Fix compile warning

* Fix a vtune warning

* Fix pooling tests

* Fix another test warning

crates/runtime/src/lib.rs

@@ -23,10 +23,7 @@
 use anyhow::Error;
 use std::sync::atomic::{AtomicU64, AtomicUsize, Ordering};
 use std::sync::Arc;
-use wasmtime_environ::DefinedFuncIndex;
-use wasmtime_environ::DefinedMemoryIndex;
-use wasmtime_environ::FunctionLoc;
-use wasmtime_environ::SignatureIndex;
+use wasmtime_environ::{DefinedFuncIndex, DefinedMemoryIndex, HostPtr, VMOffsets};
 
 #[macro_use]
 mod trampolines;
@@ -172,15 +169,8 @@ pub trait ModuleRuntimeInfo: Send + Sync + 'static {
     /// The underlying Module.
     fn module(&self) -> &Arc<wasmtime_environ::Module>;
 
-    /// The signatures.
-    fn signature(&self, index: SignatureIndex) -> VMSharedSignatureIndex;
-
-    /// The base address of where JIT functions are located.
-    fn image_base(&self) -> usize;
-
-    /// Descriptors about each compiled function, such as the offset from
-    /// `image_base`.
-    fn function_loc(&self, func_index: DefinedFuncIndex) -> &FunctionLoc;
+    /// Returns the address, in memory, that the function `index` resides at.
+    fn function(&self, index: DefinedFuncIndex) -> *mut VMFunctionBody;
 
     /// Returns the `MemoryImage` structure used for copy-on-write
     /// initialization of the memory, if it's applicable.
@@ -198,6 +188,9 @@ pub trait ModuleRuntimeInfo: Send + Sync + 'static {
     /// Returns an array, indexed by `SignatureIndex` of all
     /// `VMSharedSignatureIndex` entries corresponding to the `SignatureIndex`.
     fn signature_ids(&self) -> &[VMSharedSignatureIndex];
+
+    /// Offset information for the current host.
+    fn offsets(&self) -> &VMOffsets<HostPtr>;
 }
 
 /// Returns the host OS page size, in bytes.