Transpile libraries

[LuisLara-UH]

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The idea here is to clone the ContractDefinition nodes of kind Library, and change its kind to Contract. This way, it does not interfere with the references to the Library node functions, and it transpiles the Library clone as a contract.

[GuyMcComb]

Could you add a test?

[LuisLara-UH]

I removed the externalize-functions, because this is only for transpile the internal and private functions which aren't referenced by public or external functions. After discussed with Rodrigo, I realized these functions are not necessary for the transpiled library, because they are not reachable.

[swapnilraj]

Are we waiting for a semantic test run or can we merge this?