Deprecate publishAllPublicationsToCentralPortal()

[martinbonnin]

The same functionality can be acheived using the aggregation:

plugins {
  id("com.gradleup.nmcp") // for exposing all the publications
  id("com.gradleup.nmcp.aggregation") // for configuring the aggregation
}

nmcpAggregation {
  centralPortal {
    username.set("")
    password.get("")
    publishAllChecksums.set(true)
  }
}

dependencies {
  nmcpAggregation(project)
}

This makes for a clearer separation of concerns and will make the plugin maintainance easier moving forward.