[C++] Implement casts between time32 and time64

[asfimport]

Reporter: Wes McKinney / @wesm
Assignee: Licht Takeuchi / @Licht-T

Related issues:

• [C++] Type casting function kernel suite (Is contained by)

_{Note: This issue was originally created as ARROW-1483. Please see the migration documentation for further details.}

[asfimport]

Licht Takeuchi / @Licht-T:
@wesm Seems fixed by my PR. But tests do not exist. I will add some tests.

>>> a = pa.array(np.array([1000, 2000, 3000], dtype='int64'), type=pa.time64('us'))
>>> a.cast(pa.time32('ms'))
<pyarrow.lib.Time32Array object at 0x112cb7f18>
[
  datetime.time(0, 0, 0, 1000),
  datetime.time(0, 0, 0, 2000),
  datetime.time(0, 0, 0, 3000)
]
>>>
>>>
>>> b = pa.array(np.array([1, 2, 3], dtype='int32'), type=pa.time32('ms'))
>>> b.cast(pa.time64('us'))
<pyarrow.lib.Time64Array object at 0x112cb7f70>
[
  datetime.time(0, 0, 0, 1000),
  datetime.time(0, 0, 0, 2000),
  datetime.time(0, 0, 0, 3000)
]

[asfimport]

Wes McKinney / @wesm:
These are tested in C++ here https://github.com/apache/arrow/blob/master/cpp/src/arrow/compute/compute-test.cc#L443. I think we can just resolve this if you agree

[asfimport]

Licht Takeuchi / @Licht-T:
@wesm Thank you! I overlooked that test! This issue should just resolved.