rust

Revise and expand on 'Component Model Concepts' section and its subsections #136

Job	Run time
build (component-model/examples/example-host)	25s
build (component-model/examples/tutorial/adder, component)	17s
build (component-model/examples/tutorial/calculator, component)	14s
build (component-model/examples/tutorial/command, component)	25s
	1m 21s

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