mtmd : add video input support (#24269)
* wip
* ok: lazy bitmap API
* remember to free lazy text
* wip
* add mtmd_helper_video
* support video input on server (base64 input)
* add MTMD_VIDEO config
* add timestamp
* update CLI
* cli: allow auto-completion for video
* add --video arg
* fix build
* update docs
* rename as suggested
