Bump jsoncons to latest release

[marcoSanti]

Summary

Bumps the danielaparker/jsoncons dependency from v1.4.3 to v1.8.1, and
includes the source/CI changes needed to keep the build and the RISC-V test
passing with the newer release.

Changes

Dependency

• CMakeLists.txt: bump jsoncons GIT_TAG from v1.4.3 → v1.8.1. - src/Parser.cpp: adapt to the updated jsoncons JSON-schema API — call schema.validate(doc) directly instead of capturing the now-unneeded [[maybe_unused]] auto status return value. Validation failures are still reported via the validation_error catch.

Multicast monitor thread-safety

• capiocl/monitor.h / src/monitors/Multicast.cpp: change the terminate flag from a plain bool to std::atomic<bool> (adding #include <atomic>), and update the commit_listener / home_node_listener signatures to take const std::atomic<bool> *terminate. This removes a data race on the shared
  termination flag. - Make the listener recvfrom non-blocking (MSG_DONTWAIT) so the loop can observe the terminate flag instead of blocking indefinitely.
• Replace the pthread_cancel + unconditional join teardown with setting terminate = true and joining only when the threads are joinable(), giving a clean, deterministic shutdown. Fixes hangs observed under RISC-V emulation.

CI (RISC-V python bindings)

• .github/workflows/python-bindings.yml: pin the run-on-arch-action riscv64 distro to ubuntu22.04 (was ubuntu_latest) for a stable image;
• test-requirements.txt: add pytest-timeout==2.4.0.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 60.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 97.93%. Comparing base (f47e240) to head (4c09461).

Files with missing lines	Patch %	Lines
src/monitors/Multicast.cpp	50.00%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #78      +/-   ##
==========================================
- Coverage   98.08%   97.93%   -0.15%     
==========================================
  Files          20       20              
  Lines        1359     1359              
  Branches      885      887       +2     
==========================================
- Hits         1333     1331       -2     
  Misses          5        5              
- Partials       21       23       +2     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.