NETOBSERV-1112: Add TCP RTT calculation to ebpf-agent and userspace. (#117)

* Add TCP Handshake based RTT calculator in ebpf by keeping track of
handshake SYN and ACK packets.

Introduces a new ebpf map for tracking incoming and outgoing packets for
RTT. Can be extended to any other way of TCP sequence tracking like TCPSecr/TCPval,
or continous TCP latency tracking and other protocols like ICMP etc.

Signed-off-by: Dushyant Behl <dushyantbehl@in.ibm.com>

* Add updated bpf bindings and protobuf

Signed-off-by: Dushyant Behl <dushyantbehl@in.ibm.com>

* Add rtt to record.go and record_test.go and fix verifier issue

Signed-off-by: Dushyant Behl <dushyantbehl@in.ibm.com>

* Add RTT to exported record as a time duration in protobuf

Signed-off-by: Dushyant Behl <dushyantbehl@in.ibm.com>

* Add flowrtt to flowlogs-dump.
Small changes to bpf rtt calculations.

Signed-off-by: Dushyant Behl <dushyantbehl@in.ibm.com>

* Add documentation on how rtt is calculated.

* Add a switch for the RTT calculation feature.
This feature will be disabled by default and can be enabled via an
environment variable ENABLE_RTT.

Signed-off-by: Dushyant Behl <dushyantbehl@users.noreply.github.com>

* Reduce the flow_sequences map in size if its not used

Signed-off-by: Dushyant Behl <dushyantbehl@users.noreply.github.com>

* Small changes and refactoring.

Signed-off-by: Dushyant Behl <dushyantbehl@users.noreply.github.com>

* Change file structure and add more documentation on RTT patch

Signed-off-by: Dushyant Behl <dushyantbehl@users.noreply.github.com>

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Signed-off-by: Dushyant Behl <dushyantbehl@in.ibm.com>
Signed-off-by: Dushyant Behl <dushyantbehl@users.noreply.github.com>