Use *.wat instead of *.wit for text files (#1901)

The `*.wit` extension is actually intended to mean "WebAssembly Instance
Type", not "WebAssembly Interface Types". The `*.wat` text format
already will have support for annotations, and wasm interface types are
just an extension of that!

crates/cli/tests/interface-types.rs

@@ -12,7 +12,7 @@ fn main() -> Result<()> {
     let dir = env::current_dir()?.join("tests/interface-types");
     for entry in dir.read_dir()? {
         let path = entry?.path();
-        if path.extension().and_then(|s| s.to_str()) != Some("wit") {
+        if path.extension().and_then(|s| s.to_str()) != Some("wat") {
             continue;
         }
         if let Some(filter) = &filter {

crates/cli/tests/reference.rs

@@ -109,8 +109,8 @@ fn runtest(test: &Path) -> Result<()> {
     if interface_types {
         let wasm = td.path().join("reference_test.wasm");
         wit_validator::validate(&fs::read(&wasm)?)?;
-        let wit = sanitize_wasm(&wasm)?;
-        assert_same(&wit, &test.with_extension("wit"))?;
+        let wat = sanitize_wasm(&wasm)?;
+        assert_same(&wat, &test.with_extension("wat"))?;
     } else {
         let js = fs::read_to_string(td.path().join("reference_test.js"))?;
         assert_same(&js, &test.with_extension("js"))?;