Is there a central Boston unpopulated location that contains all the crafting stations?
The Combat Zone is an hostile area located pretty much centrally on the map, in the Theatre District of South Boston. It's south of Swan's Pond and east of Trinity Tower.
Inside, once you get past the lobby, you have a cooking station on your left. A chemistry station can be found in the first building on the right. The first building on the left contains an armor and weapon workbench.
There's a potential companion inside and another NPC that cannot be killed, but you can avoid them completely as the stations are located pretty far from them.
Inside of Combat Zone:
For your Power Armor station, if you go a little south-east you can use Slim's workshops. There's a Power Armor station, Weapon workshop and Chemistry station. You can easily dispose of him.
Slim's workshops are located west of Hesters Consumer Robotics and south of Mass Bay Medical Center, right where my character stands:
Nukapedia has a list of all Fallout 4 settlements, which includes icons to indicate which stations are pre-built in each.
Based on that list, there are only three settlements which come already fully-equipped as you desire. Fortunately, one of them is abandoned (perfect for your anti-social character) and is accessible very early in the game.
- Red Rocket Truck Stop
- Sanctuary Hills
- The Castle
There are some other non-settlement locations which are pretty well-equipped, but none in particular come immediately to mind. Besides, anti-social or not, I'm sure your character would still like to have their go-to workstations close to a place that they can fully customize themselves and call "home". Also, it's worth noting that storage containers outside of settlements tend to be less reliable for long-term use.