feat: Add network connection retrieval for AIX platform

[Dylan-M]

Description

Implement network connection retrieval functionality for AIX platform using netstat and rmsock commands.

Part 5 of splitting #1969: net package
Depends on #1979 #1980 #1981 #1982

Changes

• Add errors import for error handling
• Implement connectionsPidMaxWithoutUidsWithContext() to retrieve network connections
• Add getAIXConnections() helper function to get all network connections
• Add getAIXConnectionsForPid() helper function to get connections for a specific process
• Add resolveAIXSockToConnection() helper function to resolve socket addresses to connection info
• Add comprehensive test suite in net_aix_test.go

Testing

All new code has been tested with comprehensive unit tests covering:

• Retrieval of all network connections
• Filtering by process ID
• TCP and UDP connection handling
• Connection maximum limits

Platform

• AIX

[shirou]

This PR is relatively small compared to the others, so I could review it. However, there are two concerns:

1. Two independent features bundled together: ProtoCounters and Connections are separate functionalities and should be in separate PRs.
2. Root privilege requirement: rmsock, which is used for resolving socket-to-PID mapping in the Connections implementation, requires root privileges. Almost every function in gopsutil works without root privileges. If a function does require elevated permissions, that needs to be well-documented and discussed before merging — it affects the expectations of all users of this library.

I'm closing this along with your other open PRs for the reasons described in #1980. I'd welcome resubmission as smaller, focused PRs with the root privilege concern addressed.