Errors when saving feature metadata fields are silently ignored

### How are you running Flagsmith

- [ ] Self Hosted with Docker
- [ ] Self Hosted with Kubernetes
- [X] SaaS at flagsmith.com
- [ ] Some other way (add details in description below)

### Describe the bug

When saving any of these changes to metadata in a feature, no error is shown and the changes are not persisted after refreshing the page:

* Erasing a required field and leaving it blank
* Setting an int field to a string
* Setting a URL field to an invalid URL

### Steps To Reproduce

1. Create a required feature metadata field
2. Create a feature and provide the required field
3. Edit the feature, and remove the value for the metadata field
4. Changes are saved, but after you refresh the page the old value is still there

### Expected behavior

Users should not be allowed to save changes to features that have invalid metadata fields (invalid type or missing value on a required field).

### Screenshots

https://github.com/Flagsmith/flagsmith/assets/829698/d88435a4-7141-4dd1-a612-ffa32fd8bc27