Forward device voice assistant to Home Assistant Coversation integration

**Is your feature request related to a problem? Please describe.**

Currently there is no way to initiate the Home Assistant Conversation integration without launching the app and then navigating to a dashboard, then clicking the hamburger dots, then selecting "Start Conversation".

This becomes very problematic, especially if you're driving, and want to use your voice to tell Home Assistant to perform an action, and is just overall a bad nested placement for a feature that I anticipate will become more important the more HA leans into this "[Year of Voice](https://www.home-assistant.io/blog/2022/12/20/year-of-voice/)".

It looks like a year ago someone asked for something similar (simplifying access to the conversations feature), but was shot down due to unrealistic expectations and complexity from the initial ask (android widgets).

**Describe the solution you'd like**

I'd like to be able to ask my phones smart assistant (Google Assistant) to pass a sentence along to the Home Assistant Conversation feature. Since Home Assistant can take a string sentence as input and perform the "Home Assistant specific" intent handling, I believe all that needs to be done is have a single "[Google Assistant Common Intent](https://developers.google.com/assistant/app)" added to the companion app.

For example, "Hey Google, ask Home Assistant to turn on the front porch lights" passes "turn on the front porch lights" to the Conversation integration, via the `conversation.process` service call, which takes in the string that the Google Assistant has already parsed.

**Describe alternatives you've considered, if any**

I looked into using a widget, however currently there isn't a widget option that launches to the conversations window, and conversations can't be embedded into a dashboard (even if they could be, I wouldn't be able to make that dashboard automatically start listening), and if I can avoid having to tap on my phone while driving, that feels like the best solution anyway.

**Additional context**