conntrack: Allow configuring multiple hash IDs to connection records

[ronensc]

Currently, we have only a single hash ID for a connection which is a hash on some selected fields.
The flow direction (i.e. "ingress" or "egress") is also added to these fields to eliminate aggregation of duplicate stats (such as bytes and packets).
This makes 2 different hashes for the same connection.
The problem is that in the console plugin we would like to group together the records of the 2 hashes.
One option to do so is to add another hash ID that excludes the flow direction field. This will generate the same hash regardless of the flow direction.
This new hash can be used in the console plugin to group records by.

[jpinsonneau]

There is an alternative about merging directions at plugin side:
netobserv/network-observability-console-plugin#311
netobserv/network-observability-console-plugin#317

That would avoid having multiple hash calculations and let the user manage observation points