Implement runtime checks for compilation settings (#3899)

* Implement runtime checks for compilation settings

This commit fills out a few FIXME annotations by implementing run-time
checks that when a `Module` is created it has compatible codegen
settings for the current host (as `Module` is proof of "this code can
run"). This is done by implementing new `Engine`-level methods which
validate compiler settings. These settings are validated on
`Module::new` as well as when loading serialized modules.

Settings are split into two categories, one for "shared" top-level
settings and one for ISA-specific settings. Both categories now have
allow-lists hardcoded into `Engine` which indicate the acceptable values
for each setting (if applicable). ISA-specific settings are checked with
the Rust standard library's `std::is_x86_feature_detected!` macro. Other
macros for other platforms are not stable at this time but can be added
here if necessary.

Closes #3897

* Fix fall-through logic to actually be correct

* Use a `OnceCell`, not an `AtomicBool`

* Fix some broken tests

tests/all/wast.rs

@@ -12,6 +12,10 @@ include!(concat!(env!("OUT_DIR"), "/wast_testsuite_tests.rs"));
 // function which actually executes the `wast` test suite given the `strategy`
 // to compile it.
 fn run_wast(wast: &str, strategy: Strategy, pooling: bool) -> anyhow::Result<()> {
+    match strategy {
+        Strategy::Cranelift => {}
+        _ => unimplemented!(),
+    }
     let wast = Path::new(wast);
 
     let simd = feature_found(wast, "simd");
@@ -26,7 +30,6 @@ fn run_wast(wast: &str, strategy: Strategy, pooling: bool) -> anyhow::Result<()>
         .wasm_module_linking(module_linking)
         .wasm_threads(threads)
         .wasm_memory64(memory64)
-        .strategy(strategy)?
         .cranelift_debug_verifier(true);
 
     if feature_found(wast, "canonicalize-nan") {