Add TLP and retransmit timeouts counters to TCP sampler

[rittme]

Problem

Add two new TCP probes:

• A probe to measure Tail Loss Probes (TLP) sent.
• A probe to measure TCP Retransmit timeouts (RTO), reflecting how congested the network is.

Solution

Added two BPF kernel probes to count TLP and RTO events.

Result

Two new metrics introduced to TCP sampler:

• tcp/ tlp
• tcp/retransmit_timeout