Adding can request tests

[BradleyOlson64]

Closes #1478

For this issue we wanted to add tests to cover three cases:

1. A cluster member seeing a Seconded message should request the candidate from the sender
2. A cluster member receiving a request should respond if the requester has not sent them any statements about the candidate
3. A cluster member should reject requests if the requester appears to know the candidate (has sent them a Seconded statement)

Case 1 is already covered by the test seconded_statement_leads_to_request in polkadot/node/network/statement-distribution/src/vstaging/tests/cluster.rs

Cases 2 and 3 are covered by the new test local_node_checks_that_peer_can_request_before_responding added in this PR

[paritytech-cicd-pr]

The CI pipeline was cancelled due to failure one of the required jobs.
Job name: test-linux-stable 2/3
Logs: https://gitlab.parity.io/parity/mirrors/polkadot-sdk/-/jobs/3665534

[mrcnski]

Looks good, but should cases 2 and 3 perhaps be separate tests? Can testing for one in the same test, affect the outcome of the other one later on?

[BradleyOlson64]

@mrcnski I think we're all fine on that front. I'm testing the two request-response behaviors on different peers, peer_a vs peer_b, so I don't think one case should effect the other.

[BradleyOlson64]

bot merge

[command-bot]

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