Support multiple connections in the client mode.

[evshary]

Solve #2142

We added the EndPoints to accept a single EndPoint or EndPoint vector.

To test the multiple connections:

RUST_LOG=zenoh_transport::unicast::establishment=debug cargo run --bin zenohd -- --cfg=transport/unicast/max_links:2
RUST_LOG=zenoh_transport::unicast::establishment=debug cargo run --example z_sub -- --cfg=transport/unicast/max_links:2 --cfg="connect/endpoints:[{strategy:'allOf',locators:['tcp/127.0.0.1:7447?rel=0','tcp/127.0.0.1:7447?rel=1']}]" -m client

Note that only 'allOf' is implemented in the PR. We leave 'oneOf' for the future.

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[codecov]

Codecov Report

❌ Patch coverage is 80.10471% with 38 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.01%. Comparing base (77507c1) to head (d4d7762).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
zenoh/src/net/runtime/orchestrator.rs	75.71%	17 Missing ⚠️
commons/zenoh-config/src/mode_dependent.rs	60.86%	9 Missing ⚠️
commons/zenoh-protocol/src/core/endpoint.rs	90.62%	6 Missing ⚠️
commons/zenoh-config/src/lib.rs	83.33%	5 Missing ⚠️
zenohd/src/main.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2320      +/-   ##
==========================================
- Coverage   74.01%   74.01%   -0.01%     
==========================================
  Files         400      400              
  Lines       60846    60991     +145     
==========================================
+ Hits        45034    45140     +106     
- Misses      15812    15851      +39     

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[OlivierHecart]

This is a change in behavior.
Coma separated values were already accepted here and were the equivalent of passing multiple -e arguments.
Let's decide if:

• we assume this behavior change and add this in a minor release
• find another separator for this case

[evshary]

I personally prefer the first one, while the second one will make usage complicated.
However, it's still fine with me if we decide on the second one.

[OlivierHecart]

I also realize that we had plans to create locator groups for peers, where peer connect to a single endpoint of each group. We need to decide if this is still something we consider and how to articulate that with the multilink thing here.

[OlivierHecart]

Another point, I don't see any changes in DEFAULT_CONFIG.json5. It would be good to have this roughly documented there.

[evshary]

Another point, I don't see any changes in DEFAULT_CONFIG.json5. It would be good to have this roughly documented there.

I thought it would make the description too complicated, so I just skipped that.
I've added it to the config now.

[evshary]

@OlivierHecart I also added some tests for the feature.
I think the CI failure is related to the outdated tide in the rest plugin, which should be fixed here.
#2176