Signal netlink errors with exceptions

[abeltrano]

Type

• Bug fix
• Feature addition
• Feature update
• Documentation
• Build Infrastructure

Side Effects

• Breaking change
• Non-functional change

Goals

• Handle errors from using netlink are surfaced and handled consistently.

Technical Details

• Add NetlinkException and NetlinkErrorCategory concepts that are compatible with std:: error handling patterns using std:;exception as the base type.
• Replace throwing the integer netlink return value with throw NetlinkException.

Test Results

• All unit tests pass.

Reviewer Focus

• None

Future Work

• I observed a one-off case where the linux-apmanager unit test hung waiting for the netlink processing thread to exit. This needs to be investigated (Bug: wifi-apmanager-linux-test-unit periodically hangs #161).

Checklist

• Build target all compiles cleanly.
• clang-format and clang-tidy deltas produced no new output.
• Newly added functions include doxygen-style comment block.