refactor(userspace/libsinsp)!: drop support to protodecoders

[jasondellaluce]

What type of PR is this?

/kind cleanup

Any specific area of the project related to this PR?

/area libsinsp

Does this PR require a change in the driver versions?

What this PR does / why we need it:

Protodecoders are an ancient internal-only code instrument for implementing protocol decoders, which was introduced with the intention of supporting many. Over ~9 years, the only implementation we had for it is implementing the syslog.* fields. So, this proposes to remove protodecoders and implement those field in a simpler, more maintainable, and performant way (with no callback tangle).

Which issue(s) this PR fixes:

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

refactor(userspace/libsinsp)!: drop support to protodecoders

[FedeDP]

/approve

[poiana]

LGTM label has been added.

Git tree hash: 83a2d94bdcab4804645890dbfeaedefb7de0bfcb

[LucaGuerra]

I see that there is a ! in the name, what's the breaking change for the consumers of libs? I assume that it is the fact that it was technically possible to use protodecoders before (but nobody did).

[LucaGuerra]

LGTM

[poiana]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: FedeDP, jasondellaluce, LucaGuerra

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[jasondellaluce]

I see that there is a ! in the name, what's the breaking change for the consumers of libs? I assume that it is the fact that it was technically possible to use protodecoders before (but nobody did).

This. You never know.