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/cookiestore.rs

@@ -6,6 +6,7 @@ use std::borrow::Cow;
 use std::collections::VecDeque;
 use std::rc::Rc;
 
+use base::IpcSend;
 use base::id::CookieStoreId;
 use cookie::{Cookie, SameSite};
 use dom_struct::dom_struct;
@@ -16,7 +17,7 @@ use ipc_channel::router::ROUTER;
 use itertools::Itertools;
 use js::jsval::NullValue;
 use net_traits::CookieSource::NonHTTP;
-use net_traits::{CookieAsyncResponse, CookieData, CoreResourceMsg, IpcSend};
+use net_traits::{CookieAsyncResponse, CookieData, CoreResourceMsg};
 use script_bindings::script_runtime::CanGc;
 use servo_url::ServoUrl;