feat(tier4_system_msgs): add command mode xxx msg

[TetsuKawa]

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Description

Adds msgs aboud command mode decider, command mode switcher, control command gate.

Remarks

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[mergify]

⚠️ The sha of the head commit of this PR conflicts with #167. Mergify cannot evaluate rules on this PR. ⚠️

[mergify]

⚠️ The sha of the head commit of this PR conflicts with #167. Mergify cannot evaluate rules on this PR. ⚠️