feat(stega): allow setting stega options on client.fetch

[stipsan]

Allows setting stega options on client.fetch, so it's easy to toggle. For example an Next.js App Router website might wish to setup everything in one place:

import {createClient} from '@sanity/client/stega'

const createClient({
  // ... other options
  stega: {
    studioUrl: 'https://my-project.sanity.studio',
    filter: props => {
      if(props.sourcePath.some((path) => path === 'metadata' || path === 'openGraph' || path === 'twitter')) {
        return false
      }
      return props.filterDefault(props)
    },
  },
})

And later toggle stega on or off based on if draftMode is true:

import { draftMode } from 'next/headers'

export default async ReactServerComponent() {
  const data = await client.fetch(query, params, {stega: {enabled: draftMode().isEnabled}})
  // You can pass a boolean as a shortcut for setting stega.enabled
  const data = await client.fetch(query, params, {stega: draftMode().isEnabled})
}

It's also useful to be able to enable the logger on specific requests:

import { draftMode } from 'next/headers'

export default async ReactServerComponent() {
  const data = await client.fetch(query, params, {
    stega: {
      logger: console,
    }
  })
}