`mill.main.server.ClientServerTests` is failing CI for `main`

[lefou]

> ./mill -i -k "{main,scalalib,testrunner,bsp}.__.test"
...
X mill.main.server.ClientServerTests.hello 10058ms 
  utest.AssertionError: assert(res2.logsFor("Interrupting after 1000ms") == Seq("server-0"))
  res2: mill.main.server.ClientServerTests.ClientResult = ClientResult(0,/home/runner/work/mill/mill/out/17875277267850301185/mill-worker-5ueiCV1J/TIqSBrxHNOAF4Ax630=-1,/home/runner/work/mill/mill/out/17875277267850301185,hello WORLD
  ,HELLO WORLD
  )
    utest.asserts.Asserts$.assertImpl(Asserts.scala:30)
    mill.main.server.ClientServerTests$.$anonfun$tests$3(ClientServerTests.scala:146)
    utest.asserts.Asserts.retry(Asserts.scala:96)
    utest.asserts.Asserts.retry$(Asserts.scala:95)
    utest.package$.retry(package.scala:8)
    mill.main.server.ClientServerTests$.$anonfun$tests$2(ClientServerTests.scala:125)
...
1 targets failed
main.server.test.test 1 tests failed: 
  mill.main.server.ClientServerTests mill.main.server.ClientServerTests.hello

[lihaoyi]

Seems like flakiness looking at the commit history run results

[lihaoyi]

Added some retries so hopefully it'll be a bit more stable