More PR feedback changes.

* More use of `anyhow`.
* Change `make_accessible` into `protect_linear_memory` to better demonstrate
  what it is used for; this will make the uffd implementation make a little
  more sense.
* Remove `create_memory_map` in favor of just creating the `Mmap` instances in
  the pooling allocator. This also removes the need for `MAP_NORESERVE` in the
  uffd implementation.
* Moar comments.
* Remove `BasePointerIterator` in favor of `impl Iterator`.
* The uffd implementation now only monitors linear memory pages and will only
  receive faults on pages that could potentially be accessible and never on a
  statically known guard page.
* Stop allocating memory or table pools if the maximum limit of the memory or
  table is 0.

crates/runtime/src/instance/allocator.rs

@@ -549,8 +549,10 @@ impl OnDemandInstanceAllocator {
         let mut memories: PrimaryMap<DefinedMemoryIndex, _> =
             PrimaryMap::with_capacity(module.memory_plans.len() - num_imports);
         for plan in &module.memory_plans.values().as_slice()[num_imports..] {
-            memories
-                .push(Memory::new_dynamic(plan, creator).map_err(InstantiationError::Resource)?);
+            memories.push(
+                Memory::new_dynamic(plan, creator)
+                    .map_err(|e| InstantiationError::Resource(e.to_string()))?,
+            );
         }
         Ok(memories)
     }