Port StorageThreadMsg to GenericChannel (#38932)

This change includes the following additions to GenericChannel:
- Add a GenericSend trait which is meant to replace the `IpcSend` trait
over time, as channels are migrated. For the time being this means, that
we often need to use `GenericSend::send()` to disambiguate from the
`IpcSend::send` function, until all usages of `IpcSend` have been
replaced.
- Add an OpaqueSender impl for GenericSender
- Add a profiled version of GenericChannel. The profiling is 1:1 the
same as for the existing profiled IPC channel, namely that only the
blocked time during `recv` is measured.


Testing: No functional changes, covered by existing tests
Part of #38912

---------

Signed-off-by: Jonathan Schwender <schwenderjonathan@gmail.com>

components/shared/profile/generic_channel.rs

@@ -0,0 +1,53 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * 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::generic_channel;
+use serde::{Deserialize, Serialize};
+
+use crate::time::{ProfilerCategory, ProfilerChan};
+use crate::time_profile;
+
+pub struct GenericReceiver<T>
+where
+    T: for<'de> Deserialize<'de> + Serialize,
+{
+    receiver: generic_channel::GenericReceiver<T>,
+    time_profile_chan: ProfilerChan,
+}
+
+impl<T> GenericReceiver<T>
+where
+    T: for<'de> Deserialize<'de> + Serialize,
+{
+    pub fn recv(&self) -> Result<T, generic_channel::ReceiveError> {
+        time_profile!(
+            ProfilerCategory::IpcReceiver,
+            None,
+            self.time_profile_chan.clone(),
+            move || self.receiver.recv(),
+        )
+    }
+
+    pub fn try_recv(&self) -> Result<T, generic_channel::TryReceiveError> {
+        self.receiver.try_recv()
+    }
+
+    pub fn into_inner(self) -> generic_channel::GenericReceiver<T> {
+        self.receiver
+    }
+}
+
+pub fn channel<T>(
+    time_profile_chan: ProfilerChan,
+) -> Option<(generic_channel::GenericSender<T>, GenericReceiver<T>)>
+where
+    T: for<'de> Deserialize<'de> + Serialize,
+{
+    let (sender, receiver) = generic_channel::channel()?;
+    let profiled_receiver = GenericReceiver {
+        receiver,
+        time_profile_chan,
+    };
+    Some((sender, profiled_receiver))
+}