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/idbrequest.rs

@@ -5,12 +5,12 @@
 use std::cell::Cell;
 use std::iter::repeat_n;
 
+use base::IpcSend;
 use dom_struct::dom_struct;
 use ipc_channel::router::ROUTER;
 use js::jsapi::Heap;
 use js::jsval::{DoubleValue, JSVal, ObjectValue, UndefinedValue};
 use js::rust::HandleValue;
-use net_traits::IpcSend;
 use net_traits::indexeddb_thread::{
     AsyncOperation, AsyncReadOnlyOperation, BackendError, BackendResult, IndexedDBKeyType,
     IndexedDBRecord, IndexedDBThreadMsg, IndexedDBTxnMode, PutItemResult,