add custom commands into master data dict v2

[alisitsyn]

Description

The PR adds a way to use custom commands commands in Master data dictionary. The optional fields in data dictionary with the permissions PAR_PERMS_READ_WRITE_CUST_CMD can be used to define the custom commands associated with each CID.
This will not break existing functionality of stack and data dictionary.
It has relationship with other MR (is in progress) which will add the registration of custom function handlers for Modbus Master and slave. The registration of the new command handlers is not public functionality but can be accessible from user application.

Related

IDFGH-12046
IDFGH-10913
IDFGH-11919

Testing

Test is prepared as part of example test sequence to send command 0x06 - Read Single Holding Register.

Checklist

• 🚨 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.