feat(ops): Fast zero copy string arguments (#16777)

Uses SeqOneByteString optimization to do zero-copy `&str` arguments in
fast calls.

- [x] Depends on https://github.com/denoland/rusty_v8/pull/1129
- [x] Depends on
https://chromium-review.googlesource.com/c/v8/v8/+/4036884
- [x] Disable in async ops
- [x] Make it work with owned `String` with an extra alloc in fast path.
- [x] Support `Cow<'_, str>`. Owned for slow case, Borrowed for fast
case

```rust
#[op]
fn op_string_len(s: &str) -> u32 { 
  str.len() as u32 
}
```

1 files changed, 31 insertions, 3 deletions

diff --git a/ops/lib.rs b/ops/lib.rs
index 598350167..26fcb2a78 100644
--- a/ops/lib.rs
+++ b/ops/lib.rs
@@ -400,7 +400,12 @@ fn codegen_arg(
     return quote! { let #ident = (); };
   }
   // Fast path for `String`
-  if is_string(&**ty) {
+  if let Some(is_ref) = is_string(&**ty) {
+    let ref_block = if is_ref {
+      quote! { let #ident = #ident.as_ref(); }
+    } else {
+      quote! {}
+    };
     return quote! {
       let #ident = match #core::v8::Local::<#core::v8::String>::try_from(args.get(#idx as i32)) {
         Ok(v8_string) => #core::serde_v8::to_utf8(v8_string, scope),
@@ -408,6 +413,18 @@ fn codegen_arg(
           return #core::_ops::throw_type_error(scope, format!("Expected string at position {}", #idx));
         }
       };
+      #ref_block
+    };
+  }
+  // Fast path for `Cow<'_, str>`
+  if is_cow_str(&**ty) {
+    return quote! {
+      let #ident = match #core::v8::Local::<#core::v8::String>::try_from(args.get(#idx as i32)) {
+        Ok(v8_string) => ::std::borrow::Cow::Owned(#core::serde_v8::to_utf8(v8_string, scope)),
+        Err(_) => {
+          return #core::_ops::throw_type_error(scope, format!("Expected string at position {}", #idx));
+        }
+      };
     };
   }
   // Fast path for `Option<String>`
@@ -618,14 +635,25 @@ fn is_result(ty: impl ToTokens) -> bool {
   }
 }
 
-fn is_string(ty: impl ToTokens) -> bool {
-  tokens(ty) == "String"
+fn is_string(ty: impl ToTokens) -> Option<bool> {
+  let toks = tokens(ty);
+  if toks == "String" {
+    return Some(false);
+  }
+  if toks == "& str" {
+    return Some(true);
+  }
+  None
 }
 
 fn is_option_string(ty: impl ToTokens) -> bool {
   tokens(ty) == "Option < String >"
 }
 
+fn is_cow_str(ty: impl ToTokens) -> bool {
+  tokens(&ty).starts_with("Cow <") && tokens(&ty).ends_with("str >")
+}
+
 enum SliceType {
   U8,
   U8Mut,