React hooks test case part 2 -- useMemo

[chenesan]

Related to #2011 .

Add useMemo test cases in both shallow and mount test suites to make sure it works with enzyme. There are 2 tests for each:

1. In component get memoized value from useMemo and pass it down to child. Then rerender the component by changing a prop which is not in the dependencies of useMemo call. So we can assert that the prop passed down will be the same (===) between two rendering. Note that the memoized value is an object in the test so we can make sure they are shallow equal.
2. Like (1), but we change a prop which is in dependencies of useMemo, so now the prop passed down will be different between two rendering.
   Any advice on additional tests is welcome :-)