storage: Move shared functionality to base (#39419)

Part of #39418. See that PR for a full description.

Moves:
- `read_json_from_file`
- `write_json_to_file`
- `IpcSendResult`
- `IpcSend`

Renames:
- `CoreResourceThreadPool` to `ThreadPool` (shorter and more
descriptive, as we use it for more than the core resource thread now)

Signed-off-by: Ashwin Naren <arihant2math@gmail.com>

components/script/dom/idbopendbrequest.rs

@@ -2,11 +2,11 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
+use base::IpcSend;
 use dom_struct::dom_struct;
 use ipc_channel::router::ROUTER;
 use js::jsval::UndefinedValue;
 use js::rust::HandleValue;
-use net_traits::IpcSend;
 use net_traits::indexeddb_thread::{BackendResult, IndexedDBThreadMsg, SyncOperation};
 use profile_traits::ipc;
 use script_bindings::conversions::SafeToJSValConvertible;