[YSQL] Detect violation of clock error bounds as determined by the NTP clock.

[pao214]

Jira Link: DB-11468

Description

Motivation

We wish to use NTP based physical clocks for hybrid timestamps in YugabyteDB (see #21963). NTP based clock error bounds are more precise than the 500ms that we use with the default timestamping mechanism. However, we may run into issues if NTP is not configured correctly. We need a way to detect suboptimal NTP configurations.

Objective

We already do some preliminary checks at startup, but we need a mechanism to verify any issues at runtime for NTP clocks. Here, we rely on much more precise uncertainty windows, and it is best to add additional checks at runtime.

Proposal

Crash when hybrid time exceeds the global limit on receipt of any new message. Protect this under a gflag (and the autoflag for NTP clock) to limit the performance impact of this change.

Issue Type

kind/bug

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[pao214]

Included as part of #21963