Move VolumeNameGenerator to Aspire.Hosting

[DamianEdwards]

Description

Follow up on https://github.com/dotnet/aspire/pull/7374/files#r1946002856

Checklist

• Is this feature complete?
  • Yes. Ready to ship.
• Are you including unit tests for the changes and scenario tests if relevant?
  • No
• Did you add public API?
  • Yes
    • If yes, did you have an API Review for it?
      • Yes
    • Did you add <remarks /> and <code /> elements on your triple slash comments?
      • Yes
• Does the change make any security assumptions or guarantees?
  • No
• Does the change require an update in our Aspire docs?
  • No