Draft: Switch to Near-Zero Downtime Update terminology

What does this MR do?

MR updates the terminology used for Zero Downtime Updates to Near-Zero Downtime Updates.

This name reflects the process much more clearly as it's essentially impossible in distributed environment to achieve an upgrade completely free of downtime - There will always be brief moments where some downtime occurs, such as the time when a Load Balancer health checks take time to kick in or for a HA process to failover.

Related issues

Closes #326519 (closed)

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