Add OpenTherm component

[olegtarasov]

What does this implement/fix?

This PR adds a new component that allows ESPHome to communicate with OpenTherm devices via a hardware bridge.

OpenTherm (OT) is a standard communications protocol used in central heating systems for the communication between a central heating appliances and a thermostatic controller.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Other

Pull request in esphome-docs with documentation (if applicable): esphome/esphome-docs#3800

Test Environment

• ESP32
• ESP32 IDF
• ESP8266
• RP2040
• BK72xx
• RTL87xx

Example entry for config.yaml:

# An extremely minimal configuration which only enables you to set the boiler's
# water temperature setpoint as a number.

esphome:
  name: thermostat-number-minimal

esp8266:
  board: d1_mini

opentherm:
  in_pin: 21
  out_pin: 26

number:
  - platform: opentherm
    t_set:
      name: "Boiler Control setpoint"

Checklist:

• The code change is tested and works locally.
• Tests have been added to verify that the new code works (under tests/ folder).

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in esphome-docs.

[probot-esphome]

Hey there @olegtarasov,
Thanks for submitting this pull request! Can you add yourself as a codeowner for this integration? This way we can notify you if a bug report for this integration is reported.
In __init__.py of the integration, please add:

CODEOWNERS = ["@olegtarasov"]

And run script/build_codeowners.py

_{^{(message by NeedsCodeownersLabel)}}

[olegtarasov]

Closing this pull request in order to squash commits, will open a new one.

[olegtarasov]

New PR: #6645