Unix date fields should be numeric fields instead of Date

[Giorgi]

Description

The fields that return Unix dates should not be Date type:

To Reproduce

Steps to reproduce the behavior:

Run the following query:

{
  launchesPast(limit: 10) {
    mission_name
    launch_date_local
    launch_date_unix
    launch_date_utc
  }
}

The launch_date_unix returns numbers (as it is a Unix time) but other fields return Date:

Expected behavior

The Date fields return data in a consistent way