exporter/datadogexporter: enhance example

[gbbr]

This change improves the collector.yaml example to contain information about container tags and metrics.

needs changes on tests

[mx-psi]

-- FAIL: TestExamples (0.06s)
    --- FAIL: TestExamples/collector.yaml (0.03s)
        examples_test.go:48: 
            	Error Trace:	/home/runner/work/opentelemetry-collector-contrib/opentelemetry-collector-contrib/exporter/datadogexporter/examples_test.go:48
            	Error:      	Received unexpected error:
            	            	cannot unmarshal the configuration: 1 error(s) decoding:
            	            	
            	            	* error decoding 'receivers': unknown type: "docker_stats" for id: "docker_stats" (valid values: [otlp hostmetrics filelog])
            	Test:       	TestExamples/collector.yaml
            	Messages:   	All yaml config must validate. Please ensure that all necessary component factories are added in newTestComponents()

you need to add the component factory

[mx-psi]

Needs addressing checks CI:

Replace statements are out of date, please run "make crosslink" and commit the changes in this PR.

[songy23]

Need a make gotidy