[host] Improve host to a full blown target platform instead of just for testing

[maringeph]

Describe your idea

I'm currently trying to improve the host platform by building support for OTA over SSH.
This component uploads the host program over SSH and handles the SystemD service.
It still feels a bit hacky (enrolling ssh keys, use_address without wifi or ethernet) and isn't ready for a PR yet.
https://github.com/maringeph/esphome/tree/ota_ssh

Some things i noticed during devolvement:

• host excludes OTA -> I specifically excluded OTA over SSH from this exclusion.
• use_address can't be set in network - wifi or ethernet make no sense -> added use_address to host

@jesserockz
Before building in a completely wrong direction, i want to ask you about your opinion on this.

Are you interested in this or will this never become a part of ESPHome?

How should i handle OTA?

• The way i did it, but improve it
• Leaving host as is (for local testing) and create a new platform (linux / remote_host)
• Create an installable Application where ESPHome can upload via ESPHome OTA to

How should i handle use_address?

• Add it to host
• Get it from the OTA component (more changes in core)
• Add it to network - How should i handle it, if it's configured in network and wifi?

Should the enrollment of SSH keys be integrated in the UI?

Why is this exciting?

• Automatons for ESP32 and Raspberry Pi can all be done in ESPHome.
• ESPHome works great with HomeAssistant. No need to integrate everything by hand.

Potential use cases

• Very big ESPHome Programs
• ESPHome for Raspberry Pi

Anything else?

RS485 Communication over USB already works.

Other things i may try to get them working for host:

• GPIO (Raspberry Pi 5)
• Audio (porting to Pipewire)
• Bluetooth (porting to D-Bus API? I don't know yet)