esp32_camera: lock and unlock i2c bus around any ops that might access it

[jepler]

Now, if the i2c bus is locked, camera operations that might access the bus will raise an exception instead of using the bus without taking the lock.

Testing performed:

• ran a random demo on esp32-s3-eye
• in repl, verified that when the bus is locked the error is raised, and not otherwise

>>> i = board.I2C()
>>> cam = ...
>>> cam.vflip
False
>>> i.try_lock()
True
>>> cam.vflip
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
OSError: [Errno 11] EAGAIN
>>> i.unlock()
>>> cam.vflip
False

Closes: #6837
Closes: #6836

[microdev1]

LGTM!