Add reliability to UDP link via unsecure QUIC

[oteffahi]

Description

This PR adds the ability for UDP links to leverage unsecure QUIC (QUIC with no authentication and no encryption) to achieve reliability and inherit Zenoh's supported QUIC features (notably multistream added in #2189).

This is exposed to users by adding the ?rel=1 metadata to the endpoint (ex: udp/localhost:7447?rel=1).
The default behavior remains unreliable UDP: udp/localhost:7447 will create a raw UDP connection compatible with previous versions of Zenoh UDP link.

When enabled, this feature is not wire-compatible with UDP links of previous versions, nor with UDP listeners/clients initialized with ?rel=0 or without explicit ?rel=1.

Depends on #2429

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🏷️ Label-Based Checklist

Based on the labels applied to this PR, please complete these additional requirements:

Labels: new feature

🆕 New Feature Requirements

Since this PR adds a new feature:

• Feature scope documented - Clear description of what the feature does and why it's needed
• Minimum necessary code - Implementation is as simple as possible, doesn't overcomplicate the system
• New APIs well-designed - Public APIs are intuitive, consistent with existing APIs
• Comprehensive tests - All functionality is tested (happy path + edge cases + error cases)
• Examples provided - Usage examples in code comments or separate example files
• Documentation added - New docs explaining the feature, its use cases, and API
• Feature flag considered - Can the feature be enabled/disabled for gradual rollout?
• Performance impact assessed - Memory, CPU, storage implications measured
• Integration tested - Feature works with existing features

Consider: Can this feature be split into smaller, incremental PRs?

Instructions:

1. Check off items as you complete them (change - [ ] to - [x])
2. The PR checklist CI will verify these are completed

This checklist updates automatically when labels change, but preserves your checked boxes.

[codecov]

Codecov Report

❌ Patch coverage is 87.99157% with 171 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.87%. Comparing base (1ccdaf9) to head (0d0fdd6).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
io/zenoh-link-commons/src/quic/plaintext.rs	77.58%	39 Missing ⚠️
io/zenoh-link-commons/src/quic/unicast.rs	92.50%	30 Missing ⚠️
io/zenoh-links/zenoh-link-udp/src/reliability.rs	80.34%	23 Missing ⚠️
io/zenoh-links/zenoh-link-quic/src/unicast.rs	71.42%	18 Missing ⚠️
io/zenoh-link-commons/src/quic/utils.rs	87.38%	14 Missing ⚠️
...enoh-links/zenoh-link-quic_datagram/src/unicast.rs	68.29%	13 Missing ⚠️
io/zenoh-links/zenoh-link-udp/src/unicast.rs	80.64%	6 Missing ⚠️
io/zenoh-links/zenoh-link-serial/src/unicast.rs	0.00%	4 Missing ⚠️
...enoh-links/zenoh-link-unixpipe/src/unix/unicast.rs	0.00%	4 Missing ⚠️
io/zenoh-links/zenoh-link-vsock/src/unicast.rs	0.00%	4 Missing ⚠️
... and 8 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2430      +/-   ##
==========================================
+ Coverage   72.50%   72.87%   +0.36%     
==========================================
  Files         390      394       +4     
  Lines       63351    64358    +1007     
==========================================
+ Hits        45931    46898     +967     
- Misses      17420    17460      +40     

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