Add new total usage hours sensor

Adds a new sensor that tracks usage hours of the printer. The sensor starting value can be set during initial setup or later by the configuration flow to reset it for an already configured printer or to adjust its value if/when it has drifted over time vs what the printer says.

What's Changed

• Make options more resilient by @AdrianGarside in #430
• Add total hours estimate sensor by @AdrianGarside in #432

Full Changelog: v2.0.10...v2.0.11