(gladia & soniox): add translation support

[tinalenguyen]

add input_language and input_text to SpeechData and add translation support for gladia and soniox

closes #4943 and #4402

to test, iterate through STT node:

async def stt_node(
        self, audio: AsyncIterable, model_settings: ModelSettings
    ) -> AsyncIterable[stt_module.SpeechEvent]:
        async for event in Agent.default.stt_node(self, audio, model_settings):
            if isinstance(event, stt_module.SpeechEvent) and event.alternatives:
                alt = event.alternatives[0]
                if alt.input_language:
                    logger.info(
                        f"[STT translation] input_language={alt.input_language}, "
                        f"language={alt.language}, "
                        f"input_text={alt.input_text!r}, text={alt.text!r}"
                    )
            yield event

[chenghao-mou]

lgtm. One small thing I noticed is that the translation works with code-switching, but the source/input language only supports one value.

[chenghao-mou]

nit: borrowing terms from machine translation terminology, we should name them source_language, and source_text.

[tinalenguyen]

I renamed to source_languages and source_texts, for the polyglots

[chenghao-mou]

I don't think we need to reset this here