Welcomne to the forum.
There are no such dashcam i know off, there are solar USB power banks, and some people do use a power bank for powering a camera during parking.
But it is not a route i would go down as i dont think it is safe in the extreme heat of a parked car, and also use of a power bank in general mean you just record all the time, something that is not good for a dashcam not least in really hot environments, so thats why things like time lapse or at least low bitrate have come about to minimize internal heat generation during parking guard.
Hard wire a dashcam are in most cases a job that leave no footprint when removed, cuz all you have to do is pull the 1 or 2 piggy back fuses, and put the original fuses back in their place, and then take the ground connection off what ever screw you are using for that.
In most cases it is also pretty easy to route the wire along the headliner and down a A - pillar, or the door rubber weather seal.
You will at times see solar powered CCTV cameras or other gadgets, here for instance road / environmental measuring stations along roads are often powered by a small solar panel.
And i am sure those are the battery and solar panel + charger standing alone, and the other stuff wired to the battery.