Only render Sensor Form in flexContext Form Option For certain fields

[joshuaunity]

Description

This PR mainly targets the flexContext fields:

1. consumption-price
2. production-price
3. inflexible-device-sensors

When any of these fields are selected on the form for adding sensors is rendered as adding a fixed value in any of these field currently could break the code. So to avoid confusion to users, the fixed value option will be removed on the UI level.

Look & Feel

Before:

After:

How to test

1. Go to these assets page and select any assets(preferably one with senors)
2. Go the the flexContext Modal form(Part of the Edit options on the side)
3. Click on the edit button for flexContext
4. click on any of the mentioned fields above and confirm that only the sensor form is being rendered for it

Further Improvements

None

Related Items

This PR closes #1360

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• I agree to contribute to the project under Apache 2 License.
• To the best of my knowledge, the proposed patch is not based on code under GPL or other license that is incompatible with FlexMeasures

[nhoening]

Thanks, works great!