NETOBSERV-1478: Add eBPF Agent filtering capability (#307)

* ebpf changes to support rule based flow filtering feature

Signed-off-by: Mohamed Mahmoud <mmahmoud@redhat.com>

* flow filter feature userspace code

Signed-off-by: Mohamed Mahmoud <mmahmoud@redhat.com>

* add unit test for userspace flow filter module

Signed-off-by: Mohamed Mahmoud <mmahmoud@redhat.com>

* add flow filter doc and show some use cases

Signed-off-by: Mohamed Mahmoud <mmahmoud@redhat.com>

* create specific metics for flow filtering instead of using drop flows metric

Signed-off-by: Mohamed Mahmoud <mmahmoud@redhat.com>

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Signed-off-by: Mohamed Mahmoud <mmahmoud@redhat.com>