support tls in tidb-ctl

[lysu]

ref pingcap/tidb#15173

make tidb-ctl support tls if give 'ssl-cart', 'ssl-key', 'ca'

./tidb-ctl schema --ssl-cert /home/robi/tmplog/ccc/client.pem --ssl-key /home/robi/tmplog/ccc/client-key.pem --ca /home/robi/tmplog/ccc/ca.pem 
[
    {
        "id": 4611686018427397904,
        "db_name": {
            "O": "PERFORMANCE_SCHEMA",
            "L": "performance_schema"
        },
        "charset": "utf8mb4",
        "collate": "utf8mb4_bin",
        "state": 0
    },
    {
        "id": 1,
        "db_name": {
            "O": "test",
            "L": "test"
        },
        "charset": "utf8mb4",
        "collate": "utf8mb4_bin",
        "state": 5
    },
    {
        "id": 3,
        "db_name": {
            "O": "mysql",
            "L": "mysql"
        },
        "charset": "utf8mb4",
        "collate": "utf8mb4_bin",
        "state": 5
    },
    {
        "id": 4611686018427387905,
        "db_name": {
            "O": "INFORMATION_SCHEMA",
            "L": "information_schema"
        },
        "charset": "utf8mb4",
        "collate": "utf8mb4_bin",
        "state": 0
    },
    {
        "id": 4611686018427417904,
        "db_name": {
            "O": "INSPECTION_SCHEMA",
            "L": "inspection_schema"
        },
        "charset": "utf8mb4",
        "collate": "utf8mb4_bin",
        "state": 0
    },
    {
        "id": 4611686018427407904,
        "db_name": {
            "O": "METRICS_SCHEMA",
            "L": "metrics_schema"
        },
        "charset": "utf8mb4",
        "collate": "utf8mb4_bin",
        "state": 0
    }
]

---

This change is 

[jackysp]

LGTM

[imtbkcat]

LGTM