Add option to change integration time (5 or 10 ms)

[astropenguin]

The correlator module currently only supports for the integration time of 10 ms.
This issue will update the code to support for the integration time of 5 ms as well.

Note: In the current code, changing the integration time (10 → 5 ms) needs to change the following constants:

-N_UNITS_PER_SECOND = 6400
+N_UNITS_PER_SECOND = 12800
...
-N_SCANS_PER_SECOND = 100
+N_SCANS_PER_SECOND = 200
...
-N_SCANS_PER_MINUTE = 6000
+N_SCANS_PER_MINUTE = 12000
...
-UNIT_MILLISECOND = np.timedelta64(10, "ms")
+UNIT_MILLISECOND = np.timedelta64(5, "ms")