test: add test coverage for fs.truncate

Add test to check:
- for `null` as len parameter
- if error is propagated into callback if file doesn't exist
- if an error is actually thrown if len is not a number

PR-URL: https://github.com/nodejs/node/pull/23620


Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Denys Otrishko <shishugi@gmail.com>