chore(ui): fix save state in human annotations when null or invalid

[gtarpenning]

Description

https://wandb.atlassian.net/browse/WB-22273

This pr fixes 3 bugs in the human annotation flow:

1. When inputting invalid integers in the numeric fields, occasionally the save button is still allowed, which then saves the last valid number. This can be different than what is displayed.
2. After changing a value in a human feedback field, update the default to properly allow re-saving of the previous value. This re-queries for all the feedback, which should be fast, but we might need to revisit this.
3. Disable the save button when feedback is null. Specifically, when a valid input is deleted, disable the button.

Testing

[circle-job-mirror]

Preview this PR with FeatureBee: https://beta.wandb.ai/?betaVersion=c1d78815e137eff73ff3b8be37d9c0d48aaf2ea4