storage: Move storage related backend threads to their own crate (#39418)

This PR moves storage related APIs (currently just webstorage and
indexeddb) into their own crate. This reduces the congestion in the net
thread.

Related Zulip thread:
https://servo.zulipchat.com/#narrow/channel/263398-general/topic/indexedDB.20location/with/535911631

Sub PRs:
- [x] Move shared storage/net stuff to base (`IpcSend` and
`CoreResourcePool`) #39419

---------

Signed-off-by: Ashwin Naren <arihant2math@gmail.com>
Co-authored-by: Martin Robinson <mrobinson@igalia.com>

components/net/image_cache.rs

@@ -9,6 +9,7 @@ use std::sync::{Arc, Mutex};
 use std::{mem, thread};
 
 use base::id::PipelineId;
+use base::threadpool::ThreadPool;
 use compositing_traits::{CrossProcessCompositorApi, ImageUpdate, SerializableImageData};
 use imsz::imsz_from_reader;
 use ipc_channel::ipc::{IpcSender, IpcSharedMemory};
@@ -35,8 +36,6 @@ use webrender_api::{
     ImageDescriptor, ImageDescriptorFlags, ImageFormat, ImageKey as WebRenderImageKey,
 };
 
-use crate::resource_thread::CoreResourceThreadPool;
-
 // We bake in rippy.png as a fallback, in case the embedder does not provide
 // a rippy resource. this version is 253 bytes large, don't exchange it against
 // something in higher resolution.
@@ -703,7 +702,7 @@ pub struct ImageCacheImpl {
     store: Arc<Mutex<ImageCacheStore>>,
 
     /// Thread pool for image decoding
-    thread_pool: Arc<CoreResourceThreadPool>,
+    thread_pool: Arc<ThreadPool>,
 }
 
 impl ImageCache for ImageCacheImpl {
@@ -730,10 +729,7 @@ impl ImageCache for ImageCacheImpl {
                 pipeline_id: None,
                 key_cache: KeyCache::new(),
             })),
-            thread_pool: Arc::new(CoreResourceThreadPool::new(
-                thread_count,
-                "ImageCache".to_string(),
-            )),
+            thread_pool: Arc::new(ThreadPool::new(thread_count, "ImageCache".to_string())),
         }
     }