[sr-dev] [kamailio/kamailio] [Feature Request]: Add **connection** IP and Port vars (specifically for tcp_accept_haproxy=yes) (#2103)

### Description

When using Kamailio with `tcp_accept_haproxy=yes`, the `$si` and `$sp` variables have the real IP & Port information from the original connection to the LB leaving no way to access the connection IP & Port from where the packet is received from Kamailio perspective.

### Possible Solutions

Create two new pseudovariables that contain the connection IP & Port where the packet was received for use cases where `tcp_accept_haproxy=yes`.

Suggested names (but could be any): $CI and $CP meaning -> Connection IP and Connection Port.

### Example

With `tcp_accept_haproxy=yes`:

UAC (1.1.1.1:45621) -> (2.2.2.2:5060) LB **with** Proxy Protocol (3.3.3.3:57482) -> (4.4.4.4:5060) Kamailio.

``` $si = 1.1.1.1 $sp = 45621 $CI = 3.3.3.3 $CP = 57482 ```

With `tcp_accept_haproxy=no`:

UAC (1.1.1.1:45621) -> (2.2.2.2:5060) LB **without** Proxy Protocol (3.3.3.3:57482) -> (4.4.4.4:5060) Kamailio.

``` $si = 3.3.3.3 $sp = 57482 $CI = 3.3.3.3 $CP = 57482 ```

I don't think there is any way to get the `3.3.3.3:57482` IP and Port from the example above when using `tcp_accept_haproxy=yes` but I could be wrong.

Thanks! Joel.