Allow creating an analyzer which can consume both TCP and UDP traffic

[bbannier]

Currently a protocol analyzer needs to be declared to analyze either TCP or UDP traffic, and it is e.g., not possible to declare a Spicy analyzer which can analyze both TCP or UDP.

This restriction can be worked around by declaring two separate analyzers which share the same grammar, but analyze different traffic. The analyzers might even produce identical data and only differ artificially in name (e.g., OpenVPN_TCP and OpenVPN_UDP in zeek/spicy-analyzers); these names also appear in user-visible Zeek logs.

We should consider extending the EVT glue layer so protocol analyzers can be declared which could analyze both TCP and UDP.