Add System Nexus signal-with-start support (#863)

* chore: retrigger CI

* feat: apply transfer converters to System Nexus

* Add System Nexus signal with start support

* fix: avoid duplicate System Nexus header converter

* fix: install Nexgen for generation

* chore: update Nexgen to 0.2.3

* refactor: use SDK Core System Nexus WIT

* docs: correct signal-with-start changelog

* docs: classify signal-with-start fix

* refactor: make workflow interceptor types partial

* fix: address System Nexus review feedback

* Exclude tests from cloud execution requiring local server

Added CloudTestExclusion attribute to tests requiring local server configuration.

* Add CloudTestExclusion attribute to test method

Add exclusion attribute for CloudTest in TracingInterceptorTests.

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Co-authored-by: Justin Anderson <44687433+jmaeagle99@users.noreply.github.com>