Ensure coders are updatable partially in a cluster (aka add versions to coders)

[kennknowles]

Follow up ticket for the following discussion: https://lists.apache.org/thread.html/f3b2daa740075cc39dc04f08d1eaacfcc2d550cecc04e27be024cf52@%3Cdev.beam.apache.org%3E

Long story short: seems being able to update a live stream is a constraint beam must address. This implies no change in coder serialization. To do it the only way is to put a marker (like a version) otherwise the live update will be broken if part of a cluster is updated only.

This task is about ensuring we support it.

Imported from Jira BEAM-3616. Original Jira may contain additional context.
Reported by: romain.manni-bucau.

[Abacn]

This Issue is marked as Beam 3 - Milestone 1: No Code and ML focus. Please help us burning down the open blocker tasks.

• If this issue is solved, close it. If it is obsolete, close as not planned. If it is no longer necessary for Beam 3, move it out of the Milestone.

• If the work is pending, please be reminded that Milestone 1 is targeted for completion by Dec 30, 2025

• If this issue involves multiple milestones (e.g. remove a public API should first mark it as deprecated, scoped in Milestone 1; then finally remove it in Beam 3 release candidate, scoped in Milestone 3) and Milestone 1 portion has completed, consider move the Issue to Milestone 3.

[Abacn]

As Beam 3 - Milestone 1 ddl nears and no active work on this issue, move this off the milestone