Fix the typing of effects that take Channels

[kristenmills]

Use TakeableChannel and FlushableChannel instead of Channel in effect typings.

Example that this fixes

export function* mySaga() {
  const chan = yield call(makeChannel);

  try {
    while (true) {
      const act = yield take(chan);
      yield put(act);
    }
  } finally {
    if (yield cancelled()) {
      chan.close();
    }
  }
}

const makeChannel = () => eventChannel(emit => {
  emit({ type: 'Hello' })
  return () => { };
});

const channel = makeChannel();

const saga = testSaga(mySaga)
  .next().call(makeChannel)
  // Error happens here
  // Property 'put' is missing in type 'EventChannel<unknown>' but required in type 'Channel<unknown>'
  .next(channel).take(channel)

[codecov-io]

Codecov Report

Merging #313 into master will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #313   +/-   ##
=======================================
  Coverage   99.59%   99.59%           
=======================================
  Files          22       22           
  Lines         748      748           
  Branches      154      154           
=======================================
  Hits          745      745           
  Misses          3        3

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[jp928]

@kristenmills Many thanks for your PR.