Schema evolution failure when removing an intermediate base class

[makortel]

The purpose of this issue is to track the progress on resolving the schema evolution problem reported in #38999 (and replicated in cms-rntuple-work#8).

[makortel]

assign core

[makortel]

type root

[cmsbuild]

New categories assigned: core

@Dr15Jones,@makortel,@smuzaffar you have been requested to review this Pull request/Issue and eventually sign? Thanks

[cmsbuild]

A new Issue was created by @makortel Matti Kortelainen.

@makortel, @rappoccio, @sextonkennedy, @smuzaffar, @antoniovilela, @Dr15Jones can you please review it and eventually sign/assign? Thanks.

cms-bot commands are listed here

[makortel]

FYI @pcanal (this is only about creation of an issue about the problem reported in #38999 (comment) for better tracking on CMS side)