v2.3: QUIC: generate unique server_name for client connections (backport of #7260)

[mergify]

Problem

• QUIC clients reuse the same server_name for all connections which can cause QUIC tokens to be mixed up, as they are stored in a big hashmap deep inside Quinn, keyed by server_name
• This prevents features like address validation and 0RTT from working correctly
• This is especially an issue with firedancer validators due to a bug in FD. FD interprets invalid tokens incorrectly and ignores all incoming packets instead of reporting an error, thus preventing TPU connections from agave and significantly delaying reconnects.

Summary of Changes

• Generate server_name based on the SocketAddr of the peer we are connecting to, thus ensuring it is appropriate for the server.

Fixes #7197

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This is an automatic backport of pull request #7260 done by Mergify.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 88.23529% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.8%. Comparing base (bd39b9b) to head (ce3060b).
⚠️ Report is 1 commits behind head on v2.3.

Additional details and impacted files

@@            Coverage Diff            @@
##             v2.3    #7315     +/-   ##
=========================================
- Coverage    82.8%    82.8%   -0.1%     
=========================================
  Files         850      850             
  Lines      379964   379972      +8     
=========================================
- Hits       314849   314734    -115     
- Misses      65115    65238    +123     

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