[+] Fix: Validate frame types in packets to prevent protocol violations

[Sy0307]

Thanks for @NErinola.

Following the QUIC RFC, we validate frame types in packets to prevent protocol violations, as the Table 3 shows:

  Table 3 lists and summarizes information about each frame type that
   is defined in this specification.  A description of this summary is
   included after the table.

    +============+======================+===============+======+======+
    | Type Value | Frame Type Name      | Definition    | Pkts | Spec |
    +============+======================+===============+======+======+
    | 0x00       | PADDING              | Section 19.1  | IH01 | NP   |
    +------------+----------------------+---------------+------+------+
    | 0x01       | PING                 | Section 19.2  | IH01 |      |
    +------------+----------------------+---------------+------+------+
    | 0x02-0x03  | ACK                  | Section 19.3  | IH_1 | NC   |
    +------------+----------------------+---------------+------+------+
    | 0x04       | RESET_STREAM         | Section 19.4  | __01 |      |
    +------------+----------------------+---------------+------+------+
    | 0x05       | STOP_SENDING         | Section 19.5  | __01 |      |
    +------------+----------------------+---------------+------+------+
    | 0x06       | CRYPTO               | Section 19.6  | IH_1 |      |
    +------------+----------------------+---------------+------+------+
    | 0x07       | NEW_TOKEN            | Section 19.7  | ___1 |      |
    +------------+----------------------+---------------+------+------+
    | 0x08-0x0f  | STREAM               | Section 19.8  | __01 | F    |
    +------------+----------------------+---------------+------+------+
    | 0x10       | MAX_DATA             | Section 19.9  | __01 |      |
    +------------+----------------------+---------------+------+------+
    | 0x11       | MAX_STREAM_DATA      | Section 19.10 | __01 |      |
    +------------+----------------------+---------------+------+------+
    | 0x12-0x13  | MAX_STREAMS          | Section 19.11 | __01 |      |
    +------------+----------------------+---------------+------+------+
    | 0x14       | DATA_BLOCKED         | Section 19.12 | __01 |      |
    +------------+----------------------+---------------+------+------+
    | 0x15       | STREAM_DATA_BLOCKED  | Section 19.13 | __01 |      |
    +------------+----------------------+---------------+------+------+
    | 0x16-0x17  | STREAMS_BLOCKED      | Section 19.14 | __01 |      |
    +------------+----------------------+---------------+------+------+
    | 0x18       | NEW_CONNECTION_ID    | Section 19.15 | __01 | P    |
    +------------+----------------------+---------------+------+------+
    | 0x19       | RETIRE_CONNECTION_ID | Section 19.16 | __01 |      |
    +------------+----------------------+---------------+------+------+
    | 0x1a       | PATH_CHALLENGE       | Section 19.17 | __01 | P    |
    +------------+----------------------+---------------+------+------+
    | 0x1b       | PATH_RESPONSE        | Section 19.18 | ___1 | P    |
    +------------+----------------------+---------------+------+------+
    | 0x1c-0x1d  | CONNECTION_CLOSE     | Section 19.19 | ih01 | N    |
    +------------+----------------------+---------------+------+------+
    | 0x1e       | HANDSHAKE_DONE       | Section 19.20 | ___1 |      |
    +------------+----------------------+---------------+------+------+

                            Table 3: Frame Types