Add missing OEM fault code, OEM diagnostic code, and 2 commands to opentherm

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

Opentherm component missing 3 important protocol features:

sensors:

An OEM-specific fault/error code
opentherm ID: 5, LB u8

An OEM-specific diagnostic/service code
opentherm id: 115, u16

and commands (can be button or switch with auto turn off):

Boiler Lock-out Reset
Opentherm ID: 4, command code: 1

CH water filling
Opentherm ID: 4, command code: 2

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

control of bowler

**Additional context**

Start by locating the OpenTherm component and its existing protocol ID handling. Check how sensor values and command controls are represented and whether tests cover them. Done means the two requested codes and two commands are exposed with the specified IDs and behavior, with relevant tests updated.

Written by the indexing model from the issue text.