Enhance OpenConfig AAA Model to Support Multiple TACACS/RADIUS Servers with Shared IP Addresses and Distinct Ports

[macb2625]

Description
The current OpenConfig AAA model specifies a single leaf for the address of authentication servers in the openconfig-aaa.yang file. This design restricts the ability to configure multiple TACACS or RADIUS servers that may share the same IP address but operate on different ports. Therefore, it is not possible to accurately represent configurations where multiple servers listen on the same IP address for different authentication and accounting purposes.

Problem Statement
In the existing model:

The address key is defined as a single IP address (oc-inet:ip-address), preventing the specification of port numbers as part of the key.

public/release/models/system/openconfig-aaa.yang

Line 263 in 868ab34

key "address";

RADIUS servers utilize distinct ports for authentication (default 1812) and accounting (default 1813) and two or more server can be configured as fallback on same IP but with different acct and auth port.
TACACS servers can operate on different ports but may also share the same IP address.
As a result, configurations with the same address but different ports cannot be accurately represented, leading to potential conflicts and limitations.

[dplore]

fixed by #1105