Winch: add support for WINCH_DELIVER action

[MAVLink's DO_WINCH command](https://github.com/ArduPilot/mavlink/blob/master/message_definitions/v1.0/common.xml) defines action "4" as "WINCH_DELIVER" meaning that winch is lowered until the package reaches the ground.

We could add support for this (perhaps using [Payload Place](https://ardupilot.org/copter/docs/mission-command-list.html#payload-place)) when using the [Daiwa winch](https://ardupilot.org/copter/docs/common-daiwa-winch.html) based on the reported tension suddenly reducing. The [Daiwa winch driver is here](https://github.com/ArduPilot/ardupilot/blob/master/libraries/AP_Winch/AP_Winch_Daiwa.h).

This enhancement request comes from [this discussion](https://github.com/ArduPilot/ardupilot/issues/23976).

Start with the MAVLink DO_WINCH definition and the Daiwa driver in libraries/AP_Winch/AP_Winch_Daiwa.h, then compare the Payload Place behavior in the linked mission-command documentation. Determine how WINCH_DELIVER should lower the package and use the reported sudden tension reduction to detect ground contact. Done means the Daiwa winch supports action 4 with behavior consistent with the requested delivery semantics.

Written by the indexing model from the issue text.