Optimize DTLS Handshake and ICE Handling for Improved Performance (#3)

1. Merge ICE and DTLS ARQ max retry options into a single handshake timeout.
2. Utilize DTLS server role to prevent ARQ, as the peer DTLS client will handle ARQ.
3. Replace IO from DTLSContext with a callback function.
4. Measure and analyze the time cost for each step in the process.
5. Implement DTLS BIO callback for packet fragmentation using BIO_set_callback.
6. Generate private key and certificate prior to ICE for faster handshake.
7. Refine DTLS MTU settings using SSL_set_mtu and DTLS_set_link_mtu.
8. Provide callback for DTLS state, returning errors when DTLS encounters issues or closes.
9. Consolidate ICE request/response handling and DTLS handshake into a single function.

doc/muxers.texi

@@ -1361,21 +1361,9 @@ This muxer supports the following options:
 
 @table @option
 
-@item ice_arq_max @var{integer}
-Set the maximum number of retransmissions for the ICE ARQ mechanism.
-Default value is 5.
-
-@item ice_arq_timeout @var{integer}
-Set the start timeout in milliseconds for the ICE ARQ mechanism.
-Default value is 30.
-
-@item dtls_arq_max @var{integer}
-Set the maximum number of retransmissions for the DTLS ARQ mechanism.
-Default value is 5.
-
-@item dtls_arq_timeout @var{integer}
-Set the start timeout in milliseconds for the DTLS ARQ mechanism.
-Default value is 50.
+@item handshake_timeout @var{integer}
+Set the timeout in milliseconds for ICE and DTLS handshake.
+Default value is 5000.
 
 @item pkt_size @var{integer}
 Set the maximum size, in bytes, of RTP packets that send out.