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/idbtransaction.rs

@@ -5,9 +5,9 @@
 use std::cell::Cell;
 use std::collections::HashMap;
 
+use base::IpcSend;
 use dom_struct::dom_struct;
 use ipc_channel::ipc::IpcSender;
-use net_traits::IpcSend;
 use net_traits::indexeddb_thread::{IndexedDBThreadMsg, KeyPath, SyncOperation};
 use profile_traits::ipc;
 use script_bindings::codegen::GenericUnionTypes::StringOrStringSequence;