Remove some allocations in CodeMemory (#3253)

* Remove some allocations in `CodeMemory`

This commit removes the `FinishedFunctions` type as well as allocations
associated with trampolines when allocating inside of a `CodeMemory`.
The main goal of this commit is to improve the time spent in
`CodeMemory` where currently today a good portion of time is spent
simply parsing symbol names and trying to extract function indices from
them. Instead this commit implements a new strategy (different from #3236)
where compilation records offset/length information for all
functions/trampolines so this doesn't need to be re-learned from the
object file later.

A consequence of this commit is that this offset information will be
decoded/encoded through `bincode` unconditionally, but we can also
optimize that later if necessary as well.

Internally this involved quite a bit of refactoring since the previous
map for `FinishedFunctions` was relatively heavily relied upon.

* comments

crates/runtime/src/instance/allocator/pooling/uffd.rs

@@ -512,7 +512,7 @@ mod test {
 
             let mut handles = Vec::new();
             let module = Arc::new(module);
-            let finished_functions = &PrimaryMap::new();
+            let functions = &PrimaryMap::new();
 
             // Allocate the maximum number of instances with the maximum number of memories
             for _ in 0..instances.max_instances {
@@ -522,7 +522,8 @@ mod test {
                             PoolingAllocationStrategy::Random,
                             InstanceAllocationRequest {
                                 module: module.clone(),
-                                finished_functions,
+                                image_base: 0,
+                                functions,
                                 imports: Imports {
                                     functions: &[],
                                     tables: &[],