refactor(core): bake single-thread assumptions into spawn/spawn_blocking (#19056)

Partially supersedes #19016.

This migrates `spawn` and `spawn_blocking` to `deno_core`, and removes
the requirement for `spawn` tasks to be `Send` given our single-threaded
executor.

While we don't need to technically do anything w/`spawn_blocking`, this
allows us to have a single `JoinHandle` type that works for both cases,
and allows us to more easily experiment with alternative
`spawn_blocking` implementations that do not require tokio (ie: rayon).

Async ops (+~35%):

Before: 

```
time 1310 ms rate 763358
time 1267 ms rate 789265
time 1259 ms rate 794281
time 1266 ms rate 789889
```

After:

```
time 956 ms rate 1046025
time 954 ms rate 1048218
time 924 ms rate 1082251
time 920 ms rate 1086956
```

HTTP serve (+~4.4%):

Before:

```
Running 10s test @ http://localhost:4500
  2 threads and 10 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    68.78us   19.77us   1.43ms   86.84%
    Req/Sec    68.78k     5.00k   73.84k    91.58%
  1381833 requests in 10.10s, 167.36MB read
Requests/sec: 136823.29
Transfer/sec:     16.57MB
```

After:

```
Running 10s test @ http://localhost:4500
  2 threads and 10 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    63.12us   17.43us   1.11ms   85.13%
    Req/Sec    71.82k     3.71k   77.02k    79.21%
  1443195 requests in 10.10s, 174.79MB read
Requests/sec: 142921.99
Transfer/sec:     17.31MB
```

Suggested-By: alice@ryhl.io
Co-authored-by: Bartek Iwańczuk <biwanczuk@gmail.com>

1 files changed, 9 insertions, 5 deletions

diff --git a/cli/tools/task.rs b/cli/tools/task.rs
index bf972e2db..37a1aa1c9 100644
--- a/cli/tools/task.rs
+++ b/cli/tools/task.rs
@@ -21,6 +21,7 @@ use indexmap::IndexMap;
 use std::collections::HashMap;
 use std::path::PathBuf;
 use std::rc::Rc;
+use tokio::task::LocalSet;
 
 pub async fn execute_script(
   flags: Flags,
@@ -59,9 +60,10 @@ pub async fn execute_script(
     let seq_list = deno_task_shell::parser::parse(&script)
       .with_context(|| format!("Error parsing script '{task_name}'."))?;
     let env_vars = collect_env_vars();
-    let exit_code =
-      deno_task_shell::execute(seq_list, env_vars, &cwd, Default::default())
-        .await;
+    let local = LocalSet::new();
+    let future =
+      deno_task_shell::execute(seq_list, env_vars, &cwd, Default::default());
+    let exit_code = local.run_until(future).await;
     Ok(exit_code)
   } else if let Some(script) = package_json_scripts.get(task_name) {
     let package_json_deps_provider = factory.package_json_deps_provider();
@@ -109,8 +111,10 @@ pub async fn execute_script(
       .with_context(|| format!("Error parsing script '{task_name}'."))?;
     let npx_commands = resolve_npm_commands(npm_resolver, node_resolver)?;
     let env_vars = collect_env_vars();
-    let exit_code =
-      deno_task_shell::execute(seq_list, env_vars, &cwd, npx_commands).await;
+    let local = LocalSet::new();
+    let future =
+      deno_task_shell::execute(seq_list, env_vars, &cwd, npx_commands);
+    let exit_code = local.run_until(future).await;
     Ok(exit_code)
   } else {
     eprintln!("Task not found: {task_name}");