Add test to ensure all functions in beamline modules are devices or fixtures

[jacob720]

Fixes #1981

Instructions to reviewer on how to test:

1. Delete fixture or device decorator in a beamline module.
2. Confirm test for that beamline fails.

Checks for reviewer

• Would the PR title make sense to a scientist on a set of release notes
• If a new device has been added does it follow the standards
• If changing the API for a pre-existing device, ensure that any beamlines using this device have updated their Bluesky plans accordingly
• Have the connection tests for the relevant beamline(s) been run via dodal connect ${BEAMLINE}

[oliwenmandiamond]

This fails due to i23

def _is_i23_machine():
    """Devices using PVA can only connect from i23 machines, due to the absence of
    PVA gateways at present.
    """
    hostname = get_hostname()
    return hostname.startswith("i23-ws") or hostname.startswith("i23-control")


@devices.factory(skip=lambda: not _is_i23_machine())
def oav_pin_tip_detection() -> PinTipDetection:
    return PinTipDetection(
        f"{PREFIX.beamline_prefix}-DI-OAV-01:",
        "pin_tip_detection",
    )

So there does seem to be a use case for defining functions in the beamline module that aren't decorated. The only solution to this is to move this function and have it be imported instead

dodal/devices/beamlines/i23/utils -> is_i23_machine()

i23.py

from dodal.devices.beamlines.i23 import is_i23_machine

@devices.factory(skip=lambda: not _is_i23_machine())
def oav_pin_tip_detection() -> PinTipDetection:
    return PinTipDetection(
        f"{PREFIX.beamline_prefix}-DI-OAV-01:",
        "pin_tip_detection",
    )