Reland "refactor(core): cleanup feature flags for js source inclusion" (#19519)

Relands #19463. This time the `ExtensionFileSourceCode` enum is
preserved, so this effectively just splits feature
`include_js_for_snapshotting` into `exclude_js_sources` and
`runtime_js_sources`, adds a `force_include_js_sources` option on
`extension!()`, and unifies `ext::Init_ops_and_esm()` and
`ext::init_ops()` into `ext::init()`.

runtime/examples/extension_with_esm/main.rs

@@ -26,7 +26,7 @@ async fn main() -> Result<(), AnyError> {
     PermissionsContainer::allow_all(),
     WorkerOptions {
       module_loader: Rc::new(FsModuleLoader),
-      extensions: vec![hello_runtime::init_ops_and_esm()],
+      extensions: vec![hello_runtime::init_ext()],
       ..Default::default()
     },
   );