feat: update failure detector document

[Copilot]

This PR updates the failure detector documentation across all language versions to reflect the changes introduced in GreptimeDB PR #7005, which refined the failure detector implementation.

Changes Made

Removed Deprecated Configuration

• Removed failure_detector.first_heartbeat_estimate option from all documentation files as this parameter is no longer used in the refined implementation

Enhanced Parameter Descriptions

Updated the descriptions for all remaining failure detector parameters to provide more technical detail and context:

• failure_detector.threshold: Now explains this is the maximum acceptable φ (phi) value before a peer is treated as failed, with guidance on tuning (lower values react faster but yield more false positives)
• failure_detector.min_std_deviation: Clarified this prevents φ from exploding due to tiny variations in heartbeat intervals, providing hypersensitivity protection
• failure_detector.acceptable_heartbeat_pause: Enhanced description explains this provides additional grace period to the learned mean interval before φ rises, helping absorb temporary network hiccups or GC pauses

Added Algorithm Context

Added explanatory comments in both English and Chinese documentation indicating that GreptimeDB uses the Phi Accrual Failure Detector algorithm to detect datanode failures, providing users with important context about the underlying mechanism.

Files Updated

• Current English documentation
• Version 0.17 English documentation
• Current Chinese documentation (中文文档)
• Version 0.17 Chinese documentation (v0.17 中文文档)

Screenshot

The documentation now accurately reflects the current implementation and provides users with better understanding of how to configure the failure detection mechanism effectively.

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Original prompt

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This section details on the original issue you should resolve

<issue_title>Update docs for feat: refine failure detector</issue_title>
<issue_description>A document change request is generated from GreptimeTeam/greptimedb#7005</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #2138

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View logs

[nicecui]

Does the content need to be applied to 0.17?

[fengjiachun]

LGTM

[fengjiachun]

Does the content need to be applied to 0.17?

No, because the options we changed have not been included in v0.17.