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#### What I did
This PR resolves sonic-net#3925.

In this PR, I enhanced the `show interfaces` command to support specific BP port information display for multi-ASIC devices, for example, T2 Chassis. It means we can use commands like `show interfaces status Ethernet-BP128 -d all` to get the status of a backplane interface, e.g. Ethernet-BP128 itself, after this PR, just like what we used to do for a specific frontend interface (plus an extra `-d all` of course).

The commands I updated for getting specific BP interface information:

- `show interfaces description`
- `show interfaces status`
- `show interfaces tpid`
- `show interfaces counters`
- `show interfaces autoneg status`
- `show interfaces link-training status`
- `show interfaces fec status`

Please note that nothing has changed when running these commands on a single-ASIC device, and nothing has changed when running these commands on a multi-ASIC device without specifying an interface. The only behavior change is when we run the above commands for a specific interface on a multi-ASIC device.

#### How I did it

#### How to verify it

We can try the following commands after this PR to see the information of the backplane interface Ethernet-BP128 itself:

- `show interfaces description Ethernet-BP128 -d all`
- `show interfaces status Ethernet-BP128 -d all`
- `show interfaces tpid Ethernet-BP128 -d all`
- `show interfaces counters -i Ethernet-BP128 -d all`
- `show interfaces autoneg status Ethernet-BP128 -d all`
- `show interfaces link-training status Ethernet-BP128 -d all`
- `show interfaces fec status Ethernet-BP128 -d all`

#### Previous command output (if the output of a command-line utility has changed)

Before this PR, when we run `show interfaces status Ethernet-BP128 -d all`, the output will be empty:

```
admin@dut:~$ show int status Ethernet-BP128 -d all
     Interface                Lanes    Speed    MTU    FEC         Alias           Vlan    Oper    Admin    Type    Asym PFC
--------------  -------------------  -------  -----  -----  ------------  -------------  ------  -------  ------  ----------
```

#### New command output (if the output of a command-line utility has changed)

After this PR, when we run `show interfaces status Ethernet-BP128 -d all`, the output will be something like the following:

```
admin@dut:~$ show int status Ethernet-BP128 -d all
     Interface                Lanes    Speed    MTU    FEC         Alias           Vlan    Oper    Admin    Type    Asym PFC
--------------  -------------------  -------  -----  -----  ------------  -------------  ------  -------  ------  ----------
Ethernet-BP128  1700,1701,1702,1703     100G   9000    N/A  Eth310-ASIC1  PortChannel38      up       up     N/A         off
```