Calibration adjustment/cleanup and refactor

[xX7]

Motivation:

Using better thermostat myself, I was unhappy with the local calibration(also saw an issue about that) and sneaked around the code.

Changes:

Refactors:

• Refactored calibration code to calibration.py
• Moved const.py bridge.py and model_quirks.py
• Using CalibrationType and CalibrationMode instead of extra const variables
• Correctly renamed FIX_CALIBRATION to AGGRESIVE_CALIBRATION
• Renamed bridge.py to delegate.py
• Removed legacy "calibration_round"

Fixes:

• Fixed model quirks of TS0601 -> Incorrect condition resulting in wrong local calibration offset
• "No Calibration" is now disabling target-temp/local calibration (wasn't working before)
• Calibration calculations generally respect the user-defined tolerance

Enhancements:

• Local calibration calculations now respect the entity's step size
• Added debug logs to quickly identify model quirk issues
• Removed old_internal and old_external temperature check/set from calibration, resulting in more eager
  calibration adjustment also on hvac_mode change. Excessive updating is avoided by comparing old != new

Related issue (check one):

• fixes Calibration incorrect #1151
• addresses "Tolerance" not working #1136

Checklist (check one):

• I did not change any code (e.g. documentation changes)
• The code change is tested and works locally. Thanks to @tungmeister

Test-Hardware list (for code changes)

• Bosch BTH-RA
• TS0601 (_TZE200_cwnjrr72)

HA Version: 2023.10.1 / OS: 10.5
Zigbee2MQTT Version: 1.33.1-1

New device mappings

No device mappings.

[KartoffelToby]

@xX7 thanks for you work! I'll review it soon! :)