Feature/master slave add custom fc handlers

[alisitsyn]

Description

This MR is to add custom modbus function handlers for master and slave communication objects. This also addresses the size of command handling tables for Modbus master and slave. This MR has relationship with the MR !96 to add support of the custom commands in data dictionary.

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title: Modbus custom command handling
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sequenceDiagram
    participant M as Master Device
    participant S as Slave Device
    participant H as Command Handler

    Note over M,H: Default Command Flow
    M->>S: Send Modbus Command (Function Code)
    S->>H: Route to Default Handler
    H-->>S: Process Command
    S-->>M: Return Response

    Note over M,H: Extended Command Flow
    M->>S: Send Custom Command (New Function Code)
    S->>H: Route to Custom Handler
    Note over H: Execute Custom Logic
    H-->>S: Process Command
    S-->>M: Return Response

    Note over M,H: Overridden Command Flow
    M->>S: Send Standard Command (Overridden Function Code)
    S->>H: Route to Override Handler
    Note over H: Execute Override Logic
    H-->>S: Process Command
    S-->>M: Return Response

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Related

Closes IDFGH-10913

Closes IDFGH-13746

Closes IDFGH-6561

IDFGH-12046 (!63)

Check list

• Add custom handling API for master and slave objects

• Update set/get wrappers in slave controller object to override command handler

• Update documentation to describe how to set and get custom handler for the command

• Update examples to address the <0x41 - Custom Command> on master and slave to transfer data

• Perform testing using robot framework on host side

• 🚨 This PR does not introduce breaking changes.

• All CI checks (GH Actions) pass.

• Documentation is updated as needed.

• Tests are updated or added as necessary.

• Code is well-commented, especially in complex areas.

• Git history is clean — commits are squashed to the minimum necessary.

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