Addressed the review comments from API Council

Following are the review comments from API Council:

(Places below that reference "s/foo/bar/" below are suggesting that "foo" be
 replaced with "bar".)

GnssClock
-- Class docs should not refer to "GPS" at the top level
-- s/InNs/Nanos/
-- s/Sec/Second/

GnssMeasurement
-- s/In// for "InUnitname"
-- s/Sec/Second/
-- s/Ms/Millis/
-- s/Deg/Degrees/
-- STATUS_GPS_LOCATION_DISABLED -> STATUS_GNSS_LOCATION_DISABLED

GnssMeasurementsEvent.Callback
-- "returns" -> "reports" in the method docs as the methods return void

LocationManager
-- register/unregisterGnssMeasurementEventCallback ->
   register/unregisterGnssMeasurementsEventCallback (plural)

GnssNavigationMessage
-- MESSAGE_TYPE_ constants -> change to just TYPE_; the "MESSAGE" is redundant
   with the class name
-- is a signed byte/short ok based on the standard here? If not consider using
   int in the public api

GnssStatus
-- Make sure @IntDef exists for the constellation type
-- Please append unit types for values returned to match GnssMeasurement methods

GnssStatusCallback
-- Please document time base/units for the time parameter of onFirstFix

Bug: 27385557
Change-Id: Ifed6a2eca3fd7ba89b3ded6964a70376235af8f4