References to known test flakes and planned fixes

[yyforyongyu]

Documentation on known test flakes that don't have short-term fixes. As a reference,

• if any of the following failures are encountered in your PR, feel free to ignore them.
• It should happen in one or at most two github jobs, otherwise, new unstableness is introduced by the PR.

Unit tests

There are quite some old (~8 years) onchain notification tests, which could be fixed if the first proposed item in #8835 is implemented.

--- FAIL: TestInterfaces (0.00s)
    --- FAIL: TestInterfaces/bitcoind_rpc_polling (71.97s)
        --- FAIL: TestInterfaces/bitcoind_rpc_polling/bitcoind-rpc-polling_single_conf_ntfn (20.03s)
            test_interface.go:96: confirmation notification never received
FAIL
FAIL    github.com/lightningnetwork/lnd/chainntnfs/test/bitcoind    71.993s
FAIL

--- FAIL: TestFilteredChainView (33.91s)
    interface_test.go:808: Testing 'bitcoind_zmq' implementation of FilteredChainView
    --- FAIL: TestFilteredChainView/bitcoind_zmq:_filtered_block_ntfns (20.22s)
        interface_test.go:196: filtered block notification didn't arrive

itest

From SendPayment in a multi-hop setup, which will be fixed in #8834.

harness_assertion.go:1078: 
            Error Trace:    /home/runner/work/lnd/lnd/lntest/harness_assertion.go:1078
                                        /home/runner/work/lnd/lnd/lntest/harness_assertion.go:1031
                                        /home/runner/work/lnd/lnd/lntest/harness.go:1877
                                        /home/runner/work/lnd/lnd/lntest/harness.go:1898
                                        /home/runner/work/lnd/lnd/itest/lnd_amp_test.go:134
                                        /home/runner/work/lnd/lnd/itest/lnd_amp_test.go:25
            Error:          Received unexpected error:
                            payment c24fd3ac669179416bf6bbe9a14e024df31b467eb4238273d54c15e89529f77f status, got IN_FLIGHT, want SUCCEEDED
            Test:           TestLightningNetworkDaemon/tranche11/101-of-156/bitcoind/sendpayment_amp_invoice/native_payaddr
            Messages:       timeout while waiting payment