rust

Revise and reorganize "Why the Component Model?" section #40

Job	Run time
build (component-model/examples/example-host)	1m 58s
build (component-model/examples/tutorial/command, component)	18s
build (component-model/examples/tutorial/calculator, component)	18s
build (component-model/examples/tutorial/adder, component)	13s
	2m 47s

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