fs: support BigInt in fs.*stat and fs.watchFile

Add the `bigint: true` option to all the `fs.*stat` methods and
`fs.watchFile`.

PR-URL: https://github.com/nodejs/node/pull/20220
Fixes: https://github.com/nodejs/node/issues/12115


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>