Implement newer RTU protocol of Growatt inverters

[djwlindenaar]

What does this implement/fix?

Newer Growatt inverters use a different set of registers. This commit adds the possibility to select RTU2 protocol as used by those newer inverters. At least the MIC series, MIN series and MAX series.

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

Related issue or feature (if applicable): fixes esphome/issues#2997

Pull request in esphome-docs with documentation (if applicable): esphome/esphome-docs#1976

Test Environment

• ESP32
• ESP32 IDF
• ESP8266

Example entry for config.yaml:

# Example config.yaml
sensor:
  - platform: growatt_solar
    update_interval: 10s
    protocol_version: RTU2
    inverter_status:
      name: "Growatt Status Code"
    phase_a:
      voltage:
          name: "Growatt Voltage Phase"
      current:
          name: "Growatt Current Phase"
      active_power:
          name: "Growatt Power Phase"
    pv1:
      voltage:
          name: "Growatt PV1 Voltage"
      current:
          name: "Growatt PV1 Current"
      active_power:
          name: "Growatt PV1 Active Power"
    active_power:
      name: "Growatt Grid Active Power"
    pv_active_power:
      name: "Growatt PV Active Power"
    frequency:
      name: "Growatt Frequency"
    energy_production_day:
      name: "Growatt Today's Generation"
    total_energy_production:
      name: "Growatt Total Energy Production"
      accuracy_decimals: 1
    inverter_module_temp:
      name: "Growatt Inverter Module Temp"

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 @leeuwte, mind taking a look at this pull request as it has been labeled with an integration (growatt_solar) you are listed as a code owner for? Thanks!
_{^{(message by CodeOwnersMention)}}

[jesserockz]

Looks good, just one minor change

[djwlindenaar]

Looks good, just one minor change

Good point... Committed.