Add int64 axis support for reduction ops. (#13891)

* Add int64 axis support for reduction ops.

This fix is a follow up to PR 13863. In PR 13863 the
program crash is fixed if int64 axis is passed to reduction ops,
e.g. reduce_sum, reduce_max, etc. However, 13863 does not
process the case of int64 support, it merely fixes the crash.

This fix adds the support for int64 axis of reduction ops.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Add int64 axis support for mean, prod, sum

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Add int64 axis support for min and max.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Add int64 axis support for reduce_all and reduce_any

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Add test cases for int64 axis support of reduce_any and reduce_all

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>