Add a ThreadPool async executor to State

If we need to use simple async code in a few places, a single executor
may be better than having several threads blocking on async code.

This should probably use the calloop executor, but that's had issues in
cosmic-workspaces, though that may not apply here.

src/state.rs

@@ -33,6 +33,7 @@ use crate::{
 use anyhow::Context;
 use calloop::RegistrationToken;
 use cosmic_comp_config::output::comp::{OutputConfig, OutputState};
+use futures_executor::ThreadPool;
 use i18n_embed::{
     DesktopLanguageRequester,
     fluent::{FluentLanguageLoader, fluent_language_loader},
@@ -211,6 +212,7 @@ pub struct Common {
     pub display_handle: DisplayHandle,
     pub event_loop_handle: LoopHandle<'static, State>,
     pub event_loop_signal: LoopSignal,
+    pub async_executor: ThreadPool,
 
     pub popups: PopupManager,
     pub shell: Arc<parking_lot::RwLock<Shell>>,
@@ -710,6 +712,7 @@ impl State {
                 display_handle: dh.clone(),
                 event_loop_handle: handle,
                 event_loop_signal: signal,
+                async_executor: ThreadPool::builder().pool_size(1).create().unwrap(),
 
                 popups: PopupManager::default(),
                 shell,