Merge pull request from GHSA-wh6w-3828-g9qf

* Unconditionally use `MemoryImageSlot`

This commit removes the internal branching within the pooling instance
allocator to sometimes use a `MemoryImageSlot` and sometimes now.
Instead this is now unconditionally used in all situations on all
platforms. This fixes an issue where the state of a slot could get
corrupted if modules being instantiated switched from having images to
not having an image or vice versa.

The bulk of this commit is the removal of the `memory-init-cow`
compile-time feature in addition to adding Windows support to the
`cow.rs` file.

* Fix compile on Unix

* Add a stricter assertion for static memory bounds

Double-check that when a memory is allocated the configuration required
is satisfied by the pooling allocator.

crates/runtime/build.rs

@@ -14,13 +14,4 @@ fn main() {
     println!("cargo:rerun-if-changed=src/helpers.c");
     build.file("src/helpers.c");
     build.compile("wasmtime-helpers");
-
-    // Check to see if we are on Unix and the `memory-init-cow` feature is
-    // active. If so, enable the `memory_init_cow` rustc cfg so
-    // `#[cfg(memory_init_cow)]` will work.
-    let family = env::var("CARGO_CFG_TARGET_FAMILY").unwrap();
-    let memory_init_cow = env::var("CARGO_FEATURE_MEMORY_INIT_COW").is_ok();
-    if &family == "unix" && memory_init_cow {
-        println!("cargo:rustc-cfg=memory_init_cow");
-    }
 }