tools: Update offline_log_viewer for serde-encoded controller logs & test it

[jcsp]

The log decoder in tools/offline_log_viewer is a very useful diagnostic. It has some hand-crafted decoding logic for decoding some controller log messages into JSON.

In 22.2, when the serde_raft_0 feature flag activates after upgrade, we'll start writing controller messages in a new serde encoding (instead of old ADL).

The metadata_viewer tool needs to understand both encodings, because upgraded systems will have a mixture of encodings in their controller logs.

This is a good time to add an automated ducktape test for the tool, that runs a cluster through some administrative operations and then checks the tool can decode the resulting controller log.

[dotnwat]

visibility for @felixguendling

[jcsp]

Related: a small start on hooking this tool into automated tests is in #5315

[jcsp]

A bunch of offline_log_viewer stuff merged since this ticket was last updated - is there still work to do?

[piyushredpanda]

@andijcr ^?

[andijcr]

Tool is updated and hooked in random_node_operation_tes.py. it should be hooked in the next upgrade test pr #8253 , but that work belongs to another ticket #7310.

Let me check the changelog for serde::version, to check that nothing is missing

[andijcr]

cmd git diff 617d042edd9795ad7c63e9c60cbfb6de02f464b1 | awk 'BEGIN {RS="\+\+\+"; ORS="\n\n=======++++++\n+++"} /serde::version<[^0]/ (a commit from october)

removing entries from test files i get this file serde_versions_mods.txt that should contains the changes where serde::version is incremented. i'll run down this later to check if something is missing