[tcgc] emit output of tcgc

[tadelesh]

Clear and concise description of the problem

it is useful to have tcgc emit the output after tcgc conversion. as tcgc could also be used as an isolate emitter, we could let it to emit a yaml file that contains the context.sdkPackage data. we could add some config to let user set the language emitter name to get the output for specific language.

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[iscai-msft]

I think this is fair, would we want to output this with --debug?

[tadelesh]

i could not get --debug from context, thus have to add another options.