TSH-18123: Add UDS support for coprocessor communication

[theJC]

Resolves: #5739 / TSH-18123

Many of Apollo's customers using coprocessor will co-locate their coprocessor with their Router instance on the same host. (ie: within the same pod in kubernetes).

This PR brings parity to coprocessor communication with the Unix Domain Sockets support that both Router request ingress AND subgraph request egress have had for some time. Bypassing the full tcp/ip network stack and allowing data transfer between the Router and the coprocessor using memory space can significantly reduce latency compared to HTTP.

This has been successfully tested locally using a Spring Boot JVM coprocessor configured to listen via UDS.

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[theJC]

@bnjjj - This is the PR I mentioned in person today.

I do have an alternative branch that I had claude write for me that if you are interested to for inspiration for potential alternative avenue that could be considered, it leverages router's services/http that already has UDS support by adapting to it instead of whats done in this PR.

Here's the potential other direction / alternative: #8389

[bnjjj]

@theJC I answered on the other PR, this one looks good but I think I would prefer to have the other implementation