Add `disable` and `enable` to Ethernet component

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

My PoE powered ESPHome devices are unreliable getting an ethernet connection if they have PoE driven inductive motors attached. I believe it is the initial current inrush.

If the Ethernet component gained the same ability to disable/enable/connected/enabled/on_connect hooks that the Wifi component has, then I could programatically reattempt the Ethernet connection have the board has stabilised rather than having it repeatedly boot loop until the initial ethernet connection happens to work.

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

I have a 5v motor driven by the 5v line which powers my ESP32 board. It is a very small motor, and doesn't normally cause a problem to board operation. However, because the Ethernet component has a hard coded delay of 300 ms in its source code, it unfortunately just happens to initialise the connection at a very unhelpful time.

If at least that 300 ms delay were configurable, that would solve my problem. Better if the Ethernet component had the same control actions as the Wifi component.

Start by comparing the Ethernet component with the WiFi component, especially their connection controls and lifecycle hooks. Determine how the existing 300 ms Ethernet initialization delay is handled. Done means Ethernet exposes the requested disable, enable, connected, enabled, and on_connect behavior, or a configurable initialization delay, with matching validation and tests where the project provides them.

Written by the indexing model from the issue text.