Remove support for `VERSION_CHECKPOINTS` translogs

[DaveCTurner]

#29227 (v6.3) introduced a new translog format version, VERSION_PRIMARY_TERM, but continued to support the previous version, VERSION_CHECKPOINTS. Since master no longer supports reading indices from such old versions, we can now drop support for the VERSION_CHECKPOINTS translog format.

[elasticmachine]

Pinging @elastic/es-distributed

[DaveCTurner]

#42782 fixes the basic behaviour, but I'm reopening this as I think we should also remove the legacy version constants and the overly-heroic error detection, instead treating all bad versions as TranslogCorruptionExceptions. See e.g. https://github.com/elastic/elasticsearch/pull/42744/files#diff-e40b686ae4cf6df3e9cdef4d9262aeb1R65