Data: Payload Control should use limits from MNT1_

The Payload Control page can be used to control a gimbal mount's target angles using slides. It seems that the limits for all 3 axis are -4500 to +4500 but these should really match the limits in the MNT1_ parameters. Note that both the names have changed (see below) and the scaling has changed from centi-degrees to degrees.

- MNT**1**_PITCH_MIN, MNT1_PITCH_MAX (in 4.2 was MNT_ANGMIN_TIL, MNT_ANGMAX_TIL in centi-degrees)
- MNT**1**_ROLL_MIN, MNT1_ROLL_MAX (in 4.2 was MNT_ANGMIN_ROL, MNT_ANGMAX_ROL in centi-degrees)
- MNT**1**_YAW_MIN, MNT1_YAW_MAX (in 4.2 was MNT_ANGMIN_PAN, MNT_ANGMAX_PAN in centi-degrees)

By the way, at some point we should consider replacing the use of the MOUNT_CONTROL message with DO_GIMBAL_MANAGER_PITCHYAW which is described [here on the wiki](https://ardupilot.org/dev/docs/mavlink-gimbal-mount.html#mav-cmd-do-gimbal-manager-pitchyaw-to-move-to-a-desired-angle-or-at-a-desired-rate).

Also instead of sending the MOUNT_CONTROL message to control the gimbal's mode it could instead send MAV_CMD_MOUNT_CONTROL (also described on the above link).

This is somewhat related to this enhancement request https://github.com/ArduPilot/MissionPlanner/issues/2906

Locate the Payload Control page and trace how its three sliders currently use fixed -4500/+4500 limits. Compare that behavior with the listed MNT1_PITCH, MNT1_ROLL, and MNT1_YAW minimum and maximum parameters and their degree scaling; done means each axis uses the corresponding configured limits. Treat the MOUNT_CONTROL and DO_GIMBAL_MANAGER discussion as separate scope unless maintainers confirm otherwise.

Written by the indexing model from the issue text.