getFieldsValue(true) allows for direct mutation of the form store

Repro:

Set up any basic form, and give a field an onChange like this:

() => {
    const formData = form.getFieldsValue(true)
    delete formData.nameOfField
    console.log(form.getFieldsValue(true))
}

Normally, one would expect that this should have no effect, as react/state context should be immutable, but in this case you will find that it will log an object missing the deleting field.

The problem comes from the implementation of getFieldsValue here:
https://github.com/react-component/field-form/blob/d7892873e9eee6e4c618d4289fcdbc9ee240f68f/src/useForm.ts#L271-L273

Which just returns the store object directly.

This should be following React conventions and returning a clone, as it does when a specific list of NamePaths is requested.

Start at src/useForm.ts around lines 271-273 and reproduce the issue with getFieldsValue(true) and deletion of a field. Confirm the returned value shares mutable state with the form store; done means deleting a field from the returned object no longer changes a later getFieldsValue(true) result, while the existing behavior for specific NamePaths remains intact.