Don't force inline slow_function_impl (#1016)

It created 2 copies of the function (normal one and one for metrics)

Size benchmark from
[`tree/objwrap_bench`](https://github.com/denoland/deno_core/tree/objwrap_bench)
```
52M dcore_baseline
63M dcore_js
81M dcore_objwrap_old
68M dcore_objwrap_new
```

Author: littledivy

ops/op2/dispatch_async.rs

@@ -156,7 +156,6 @@ pub(crate) fn generate_dispatch_async(
 
   Ok(
     gs_quote!(generator_state(info, slow_function, slow_function_metrics, opctx) => {
-      #[inline(always)]
       fn slow_function_impl<'s>(info: &'s deno_core::v8::FunctionCallbackInfo) -> usize {
         #[cfg(debug_assertions)]
         let _reentrancy_check_guard = deno_core::_ops::reentrancy_check(&<Self as deno_core::_ops::Op>::DECL);

ops/op2/dispatch_slow.rs

@@ -142,7 +142,6 @@ pub(crate) fn generate_dispatch_slow(
 
   Ok(
     gs_quote!(generator_state(opctx, info, slow_function, slow_function_metrics) => {
-      #[inline(always)]
       fn slow_function_impl<'s>(#info: &'s deno_core::v8::FunctionCallbackInfo) -> usize {
         #[cfg(debug_assertions)]
         let _reentrancy_check_guard = deno_core::_ops::reentrancy_check(&<Self as deno_core::_ops::Op>::DECL);