[WIP] Managed implementation of DNS resolver

[rzikm]

Description

This PR brings in a C# implementation of a DNS resolver that is able to signal the TTL information together with the query results.

Main features

• Async network I/O, fully cancellable
• Mockable
• Resolves IP Addresses (A/AAAA records) and Service records (SRV + related A/AAAA)
• Transparent fallback to TCP
• Autodetection of OS settings (i.e. reads nameservers from /etc/resolv.conf file)
• Thread-safe

Checklist

• Is this feature complete?
  • [ ] Yes. Ready to ship.
  • [ ] No. Follow-up changes expected.
• Are you including unit tests for the changes and scenario tests if relevant?
  • [x] Yes
  • [ ] No
• Did you add public API?
  • [ ] Yes
    • If yes, did you have an API Review for it?
      • [ ] Yes
      • [ ] No
    • Did you add <remarks /> and <code /> elements on your triple slash comments?
      • [ ] Yes
      • [ ] No
  • [x] No
• Does the change make any security assumptions or guarantees?
  • [ ] Yes
    • If yes, have you done a threat model and had a security review?
      • [ ] Yes
      • [ ] No
  • [ ] No
• Does the change require an update in our Aspire docs?
  • [ ] Yes
    • Link to aspire-docs issue:
  • [ ] No

Microsoft Reviewers: Open in CodeFlow