otel: Add OpenTelemetry functionality to NGINX Unit #882

Job	Run time
test (unit, ubuntu-latest)	1m 20s
test (go-1.21, ubuntu-latest)	1m 17s
test (go-1.22, ubuntu-latest)	1m 10s
test (java-17, ubuntu-latest)	2m 22s
test (java-18, ubuntu-latest)	2m 35s
test (java-21, ubuntu-latest)	2m 23s
test (node-20, ubuntu-latest)	59s
test (node-21, ubuntu-latest)	1m 19s
test (perl, ubuntu-latest)	41s
test (php-8.2, ubuntu-latest)	40s
test (php-8.3, ubuntu-latest)	1m 7s
test (python-3.11, ubuntu-latest)	5m 33s
test (python-3.12, ubuntu-latest)	5m 28s
test (ruby-3.2, ubuntu-latest)	53s
test (ruby-3.3, ubuntu-latest)	1m 4s
test (wasm, ubuntu-latest)	3m 6s
test (wasm-wasi-component, ubuntu-latest)	8m 27s
	40m 24s

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