Use lifecycle method names directly, rather than excluding all exported methods on DoFns.

Breaks certain usecases with extreme number (10+) of emitter parameters, when the method doesn't have a generic representation. The static code generator works in those cases, but it isn't recommended.

The ideal work around would be to have a tagged API instead of the positional one, but that's significantly more work.

Using lifecycle names directly neutered the previous verification check anyway, so we've opted to remove that entirely. Additional tests were also added to ensure the fallthrough behavior occurs.

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