fix(ui): properly extracts label from field in FieldLabel component (#8190)

Although the `<FieldLabel />` component receives a `field` prop, it does
not use this prop to extract the `label` from the field. This is
currently only an issue when rendering this component directly, such as
within `admin.components.Label`. The label simply won't appear unless
explicitly provided, despite it being passed as `field.label`. This is
not an issue when rendering field components themselves, because they
properly thread this value through as a top-level prop.

Here's an example of the issue:

```tsx
import type { TextFieldLabelServerComponent } from 'payload'

import { FieldLabel } from '@payloadcms/ui'
import React from 'react'

export const MyCustomLabelComponent: TextFieldLabelServerComponent = ({ clientField }) => {
  return (
    <FieldLabel
      field={clientField}
      label={clientField.label} // this should not be needed!
    />
  )
}
```

Here is the end result:

```tsx
import type { TextFieldLabelServerComponent } from 'payload'

import { FieldLabel } from '@payloadcms/ui'
import React from 'react'

export const MyCustomLabelComponent: TextFieldLabelServerComponent = ({ clientField }) => {
  return <FieldLabel field={clientField} />
}
```

test/fields/collections/Email/CustomLabel.tsx

@@ -1,12 +1,14 @@
 'use client'
 
+import type { EmailFieldClientComponent } from 'payload'
+
 import { useFieldProps } from '@payloadcms/ui'
 import React from 'react'
 
-export const CustomLabel = ({ schemaPath }) => {
+export const CustomLabel: EmailFieldClientComponent = ({ field }) => {
   const { path: pathFromContext } = useFieldProps()
 
-  const path = pathFromContext ?? schemaPath // pathFromContext will be undefined in list view
+  const path = pathFromContext ?? field?._schemaPath // pathFromContext will be undefined in list view
 
   return (
     <label className="custom-label" htmlFor={`field-${path.replace(/\./g, '__')}`}>