feat: nested fields and integer values for filter relation widget

[JimmyOei]

Summary

This PR for the relation widget adds functionality for nested fields in the filters and also allows integer types for the values in the filters.

• Nested fields: it is now possible to have a filter like this: filters: [ { field: 'deeply.nested.field', values: ['Some text'] } ]
• Integer type: values can now also be integers (before only booleans and strings were allowed): filters: [ { field: 'num', values: [1, 12, 20] } ]

Test plan

I added a unit test for the nested fields and for the integer type.

Checklist

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