Make it possible to disable partial updates

[andersruneson]

What does this implement/fix?

Some eink displays have issues with partial updates, this commit makes it possible to force full update on every refresh by setting full_update_every to 1.

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)
• Configuration change (this will require users to update their yaml configuraiton files to keep working)

Related issue or feature (if applicable): fixes

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

Test Environment

• ESP32
• ESP8266
• Windows
• Mac OS
• Linux

Example entry for config.yaml:

# Example config.yaml
display:
  - platform: waveshare_epaper
    id: ui_display
    cs_pin: 5
    dc_pin: 17
    busy_pin: 4
    reset_pin: 16
    model: 2.13in-ttgo
    update_interval: 120s
    full_update_every: 1
    rotation: 90

Explain your changes

There is currently no way to force a full refresh on every update. This patch solves this issue.

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.