[BUG] Failed to calibrate devices with only color cameras

[lincolnxlw]

Describe the bug
calibrate.py script failed to calibrate boards with only color cameras (OAK-1, OAK-1-Lite) or any custom boards with only rgb cameras defined.

Minimal Reproducible Example
Use the board config for OAK-1-Lite and run the calibration script by python3 calibrate.py -s 2.5 -db -brd /config/OAK-1-LITE.json.json -ih

Expected behavior
Since only color camera available in the device, calibration will only run the rgb calibration for the color camera.

Screenshots
Calibration script expecting stereo_config and get the following log

File "/depthai/calibrate.py", line 699, in capture_images_sync

leftStereo = self.board_config['cameras'][self.board_config['stereo_config']['left_cam']]['name']

KeyError: 'stereo_config'

[MaticTonin]

Hi.
Yes, I see that the program always assumes that board_config includes stereo calibration even if board does not incluce one.
You can in that case just change the lines as:

if 'stereo_config' in self.board_config['cameras']:
    leftStereo =  self.board_config['cameras'][self.board_config['stereo_config']['left_cam']]['name']
    rightStereo = self.board_config['cameras'][self.board_config['stereo_config']['right_cam']]['name']
    print(f'Left Camera of stereo is {leftStereo} and right Camera of stereo is {rightStereo}')

and try the calibration process again.

[themarpe]

@MaticTonin please open a PR with this changes such that our calibration procedure gets improved overall

[themarpe]

@lincolnxlw does that resolve your issue? Feel free to reopen otherwise