feat(ops): relational ops (#18023)

Join two independent ops into one. A fast impl of one + a slow callback
of another. Here's an example showing optimized paths for latin-1 via
fast call and the next-best fallback using V8 apis.

```rust
#[op(v8)]
fn op_encoding_encode_into_fallback(
  scope: &mut v8::HandleScope,
  input: serde_v8::Value,
// ...

#[op(fast, slow = op_encoding_encode_into_fallback)]
fn op_encoding_encode_into(
  input: Cow<'_, str>,
// ...
```

Benchmark results of the fallback path:
```
time target/release/deno run -A --unstable ./cli/tests/testdata/benches/text_encoder_into_perf.js
________________________________________________________
Executed in   70.90 millis    fish           external
   usr time   57.76 millis    0.23 millis   57.53 millis
   sys time   17.02 millis    1.28 millis   15.74 millis

target/release/deno_main run -A --unstable ./cli/tests/testdata/benches/text_encoder_into_perf.js
________________________________________________________
Executed in  154.00 millis    fish           external
   usr time   67.14 millis    0.26 millis   66.88 millis
   sys time   38.82 millis    1.47 millis   37.35 millis
```

1 files changed, 31 insertions, 21 deletions

diff --git a/ops/attrs.rs b/ops/attrs.rs
index a76cfddf6..d0182fc69 100644
--- a/ops/attrs.rs
+++ b/ops/attrs.rs
@@ -1,44 +1,54 @@
 // Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
 use syn::parse::Parse;
 use syn::parse::ParseStream;
-use syn::punctuated::Punctuated;
 use syn::Error;
 use syn::Ident;
 use syn::Result;
 use syn::Token;
 
-#[derive(Copy, Clone, Debug, Default)]
+#[derive(Clone, Debug, Default)]
 pub struct Attributes {
   pub is_unstable: bool,
   pub is_v8: bool,
   pub must_be_fast: bool,
   pub deferred: bool,
   pub is_wasm: bool,
+  pub relation: Option<Ident>,
 }
 
 impl Parse for Attributes {
   fn parse(input: ParseStream) -> Result<Self> {
-    let vars = Punctuated::<Ident, Token![,]>::parse_terminated(input)?;
-
-    let vars: Vec<_> = vars.iter().map(Ident::to_string).collect();
-    let vars: Vec<_> = vars.iter().map(String::as_str).collect();
-    for var in vars.iter() {
-      if !["unstable", "v8", "fast", "deferred", "wasm"].contains(var) {
-        return Err(Error::new(
-          input.span(),
-          "invalid attribute, expected one of: unstable, v8, fast, deferred, wasm",
-        ));
-      }
+    let mut self_ = Self::default();
+    let mut fast = false;
+    while let Ok(v) = input.parse::<Ident>() {
+      match v.to_string().as_str() {
+        "unstable" => self_.is_unstable = true,
+        "v8" => self_.is_v8 = true,
+        "fast" => fast = true,
+        "deferred" => self_.deferred = true,
+        "wasm" => self_.is_wasm = true,
+        "slow" => {
+          if !fast {
+            return Err(Error::new(
+              input.span(),
+              "relational attributes can only be used with fast attribute",
+            ));
+          }
+          input.parse::<Token![=]>()?;
+          self_.relation = Some(input.parse()?);
+        }
+        _ => {
+          return Err(Error::new(
+             input.span(),
+            "invalid attribute, expected one of: unstable, v8, fast, deferred, wasm",
+            ));
+        }
+      };
+      let _ = input.parse::<Token![,]>();
     }
 
-    let is_wasm = vars.contains(&"wasm");
+    self_.must_be_fast = self_.is_wasm || fast;
 
-    Ok(Self {
-      is_unstable: vars.contains(&"unstable"),
-      is_v8: vars.contains(&"v8"),
-      deferred: vars.contains(&"deferred"),
-      must_be_fast: is_wasm || vars.contains(&"fast"),
-      is_wasm,
-    })
+    Ok(self_)
   }
 }