Fix Frient EMI LED divisor and multiplier

[TheJulianJES]

For testing, see the comment below this one.

Proposed change

This PR sets the divisor and multiplier to fixed values to avoid possible conflicts with the interface_mode manufacturer specific attribute (0x0302, same as divisor

This PR is just for testing. On the HA forum, it was observed that the EMI LED shoots to random values for the instantaneous_demand about once a month. This is just a shot in the dark to see if this would fix that.

See:
https://community.home-assistant.io/t/frient-joins-works-with-home-assistant/926758/63?u=thejulianjes

Additional information

This is similar to the implementation done for the Frient HAN EMI:

• Fix Frient EMI Norwegian HAN divisor #4396

Tests are expected to fail for now. Apparently just using the CustomCluster causes the existing EMI LED tests to fail.
I'll fix them before this PR is merged (if at all).

BASED ON (below should to be merged first):

• Expose Frient EMI LED reset current summation button #4484

Device diagnostics

Checklist

• The changes are tested and work correctly
• pre-commit checks pass / the code has been formatted using Black
• Tests have been added to verify that the new code works
• Device diagnostics data has been attached

[TheJulianJES]

Custom quirk download link:
https://github.com/TheJulianJES/zha-device-handlers/blob/tjj/frient_emi_led_fixed_divisor/zhaquirks/develco/emi_led.py
(use GitHub's download button or view RAW and then download using the browser's save page feature)

If you want to test this as a custom quirk, you can do the following:

1. Install an addon that allows you to modify files in Home Assistant's /config directory.
   The "Samba share" addon or VSCode addon can be used for this.
2. Create a zha_custom_quirks folder in Home Assistant's /config directory. So, in the folder where HA's configuration.yaml is.
3. Use the download button on the linked GitHub page to get the custom quirk as a .py file.
4. Copy the custom quirk file you've just downloaded into the newly created zha_custom_quirks.
5. Now, add the following to HA's configuration.yaml:

zha:
  custom_quirks_path: /config/zha_custom_quirks

(Make sure you only have one zha: entry in your configuration.yaml. If you modified other ZHA YAML settings, you may need to merge your modifications with the one above.)

6. Restart Home Assistant.
7. Check if ZHA still works. if not, check the logs and post any errors.
8. Check if the custom quirk works as expected.

If you search the web, you should also be able to find some more info on installing custom quirks.