fix: race in NetworkRecepient

[matklad]

closes #6826

We have circular depedencies between PeerManager and Client, which we
break via dyn PeerManagerAdapter. As this is a real cycle, we close it
at runtime by calling set_recipient. But today nothing prevents client
from sending message to network before that, and indeed that happens if
we are unlucky with timing.

This commit fixes the issue by making PeerManagerAdapter APIs block
until the loop is closed.

---

After finishing the implementation, I realized that this might not be the ideal solution. It seems that actix has the API (Actor::create) for tying such loop nicely, where you can get actor's address before creating the actor. We use it, for example, here:

nearcore/integration-tests/src/tests/network/runner.rs

Lines 64 to 70 in d18f345

	let peer_manager = PeerManagerActor::create(move |ctx| {
	let mut client_config = ClientConfig::test(false, 100, 200, num_validators, false, true);
	client_config.archive = config.archive;
	client_config.ttl_account_id_router = config.ttl_account_id_router;
	let network_adapter = NetworkRecipient::default();
	network_adapter.set_recipient(ctx.address().recipient());
	let network_adapter = Arc::new(network_adapter);

So, in theory, we can just impl PeerManagerAdapter for Recipient<PeerManagerMessageRequest> and then rewrite all call-sites to use create and friends.

Upon closer examination, it seems that that is possible, but not trivial, as create API is not orthogonal enough.

• we use Actor::start_in_arbiter and Actor::mock, which don't have create-like alternatives. We can open-code them, but that's adding more to the framework
• ::create itself can't return something else, so that means we'd have to use .unwraps

So I think it's better to maybe do just what this PR is doing and just fix the current code.

Test Plan

Verify that, after applying the following "unfortunate timing" diff

diff --git a/tools/mock_node/src/setup.rs b/tools/mock_node/src/setup.rs
index 30940262b..9e7493cad 100644
--- a/tools/mock_node/src/setup.rs
+++ b/tools/mock_node/src/setup.rs
@@ -322,6 +322,7 @@ pub fn setup_mock_node(
                 !archival,
             )
         });
+    std::thread::sleep_ms(300);
     network_adapter.set_recipient(mock_network_actor.clone().recipient());
 
     // for some reason, with "test_features", start_http requires PeerManagerActor,

The following test

$ cargo test --package mock_node --lib -- setup::test::test_mock_node_basic --exact --nocapture

fails on master and passes with this PR applied