Run/config: allow configuring default columns for run stats table

[ol-nata]

Info

Add support for configuring which columns are displayed by default in the run stats table via the main project config. The default value matches the previous hardcoded behaviour. The stats API response is extended to include the resolved default column list alongside the existing results, so the frontend can apply it without hardcoding.

Overview of changes

Config

Added configuration parameter to control which run stats table columns are displayed by default.

API

GET /bublik/api/v2/<run ID>/stats/

Response data (default_columns added):

{
    "results": {
        "result_id": 6335,
        "exec_seqno": 1,
        "parent_id": null,
        "type": "pkg",
        "test_id": 1,
        "test_name": "dpdk-ethdev-ts",
        "period": "1781110030s230276-1781119169s529164",
        "path": [
            "dpdk-ethdev-ts"
        ],
        "objective": "",
        "children": [
        ...
        ],
        "stats": {
            "passed": 114,
            "failed": 0,
            "passed_unexpected": 0,
            "failed_unexpected": 0,
            "skipped": 198,
            "skipped_unexpected": 66,
            "abnormal": 0
        },
        "comments": []
    },
    "default_columns": [
        "run",
        "passed",
        "failed",
        "passed_unexpected",
        "failed_unexpected",
        "skipped",
        "skipped_unexpected",
        "abnormal"
    ]
}