Add socket option params to transport config in PJSUA2

[sauwming]

Continuing #3424.

There are a couple of complications with socket options in PJSUA2 level:

• The option value is passed by address.
• The option value itself must be available throughout the lifetime of the transport.

So instead, adopting a similar approach as Android API:
https://developer.android.com/reference/android/system/Os#setsockoptInt(java.io.FileDescriptor,%20int,%20int,%20int)
here we pass the option value by setting the integer value. Currently, only integer option value is supported, but this can be extensible to other types, such as timeval.

In addition, we also add API pj_sockopt_params_clone() to perform deep clone of the socket options, so app doesn't need to maintain the buffer.

[nanangizz]

If the lifetime requirement is because the setting is shallow-cloned by transport listener (to be applied to transport instances), perhaps change it to deep-clone to avoid the lifetime requirement? This sounds more like a PJSIP transport issue though.