External vercel og for nodejs runtime (#48844)
### Why
Default font file of `@vercel/og` is not loaded, because the og package is bundled by webpack and we should external it so that `fs.readFileSync` is bundled and manged that can't be traced by nft.
### How
This PR externals `@vercel/og` so that they don't need to be bundled and files can be properly traced
Closes NEXT-1047
Fixes #48704
