Dds arm through external control

[Ryanf55]

Purpose

Make arming from DDS go through external control. That way, we can prevent a companion computer from arming using #28429

We want all services that control the state of the vehicle to go through external control so we can gate them in a single place.

Size (Durandal)

Binary Name      Text [B]       Data [B]     BSS (B)      Total Flash Change [B] (%)      Flash Free After PR (B)
---------------  -------------  -----------  -----------  ----------------------------  -------------------------
arducopter-heli  72 (+0.0040%)  0 (0.0000%)  0 (0.0000%)  72 (+0.0039%)                                    141248
antennatracker   0 (0.0000%)    0 (0.0000%)  0 (0.0000%)  0 (0.0000%)                                      613396
arducopter       72 (+0.0040%)  0 (0.0000%)  0 (0.0000%)  72 (+0.0039%)                                    140792
ardurover        72 (+0.0043%)  0 (0.0000%)  0 (0.0000%)  72 (+0.0043%)                                    [29](https://github.com/ArduPilot/ardupilot/actions/runs/11826461468/job/32952516727?pr=28609#step:10:30)4832
arduplane        72 (+0.0040%)  0 (0.0000%)  0 (0.0000%)  72 (+0.0040%)                                    143680
blimp            0 (0.0000%)    0 (0.0000%)  0 (0.0000%)  0 (0.0000%)                                      591472
ardusub          0 (0.0000%)    0 (0.0000%)  0 (0.0000%)  0 (0.0000%)                                      350564

Motivation

#28429 (comment)

[tizianofiorenzani]

LGTM

[Ryanf55]

@IamPete1 I'm interested in a review/merge since this touches external control.

[IamPete1]

LGTM

[Ryanf55]

Hi @Hwurzburg , this PR has no change in user behavior. I don't think a wiki is necessary. Are you ok if I remove the label?

[Hwurzburg]

np