Add a feature flag for a failure because of an heartbeat failed check

[benmoriceau]

What

Add a feature flag that will then be used to protect jobs from failing because of a missed heartbeat.

[github-actions[bot]]

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[colesnodgrass]

@benmoriceau heads-up that the flags.yml file was moved to the root directory in #22158

[benmoriceau]

@colesnodgrass could you review the flag in LD? https://app.launchdarkly.com/default/production/features/heartbeat.failSync/targeting It is the first one, I'm creating and I would like to make sure that I didn't do a mistake.