Add support for full_update_every for Waveshare 7.5in-bV3 e-paper display in ESPHome

**Describe the problem you have/What new integration you would like**

**Please describe your use case for this integration and alternatives you've tried:**

**Additional context**

Description:

The waveshare_epaper display component in ESPHome currently supports the full_update_every parameter only for a limited set of display models. However, this parameter is not available for the 7.5in-bV3 model (model code: 7.50in-bV3), which results in ghosting and faded images after multiple partial updates.

Many users, especially those using this display for dashboards and status panels, encounter significant visual degradation over time without full updates.

In the Arduino world, this issue is mitigated using libraries such as GxEPD2, which allow for full screen refreshes to be triggered after a set number of partial updates. It would be extremely useful to have this capability natively in ESPHome, without requiring an external component.

Proposed Solution:

Extend the waveshare_epaper component to allow the full_update_every: parameter for the 7.5in-bV3 display, triggering a full refresh after N partial updates. This would match the behavior already implemented for other displays like 2.13in, 2.90in, and 7.50inV2p.

References:

ESPHome Docs – Waveshare E-Paper Display

Community discussion about ghosting

[GxEPD2 Arduino Library – Full Update Management](https://github.com/ZinggJM/GxEPD2)

Benefits:

Better long-term image quality on 7.5in-bV3 displays

No need for external component hacks

Matches user expectations and feature parity with Arduino implementations

Simplifies configuration for HA dashboards and sensor displays