tidb-cloud: update the RU definition

[qiancai]

What is changed, added or deleted? (Required)

Add the definition of RU for TiDB Cloud Dedicated and TiDB Self-Managed

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[gemini-code-assist]

Summary of Changes

Hello @qiancai, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request refines the definition of 'Request Unit (RU)' within the TiDB Cloud glossary. The primary goal is to provide a clearer understanding of how RUs are applied across different TiDB offerings, differentiating their role as a billing metric for starter plans versus a resource control mechanism for dedicated and self-managed environments. This ensures users have precise information regarding resource management and cost implications.

Highlights

• Updated RU Definition: The definition of 'Request Unit (RU)' has been significantly expanded and clarified in the TiDB Cloud glossary.
• Differentiated RU Usage: The updated definition now distinguishes between RU as a 'billing and usage metric' for TiDB Cloud Starter and as a 'resource abstraction unit' for TiDB Cloud Dedicated and TiDB Self-Managed deployments.
• Resource Control Context: For Dedicated and Self-Managed TiDB, RU is explicitly defined as representing system resource consumption (CPU, IOPS, bandwidth) for resource control, not billing.

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[gemini-code-assist]

Code Review

This pull request updates the definition of Request Unit (RU) in the TiDB Cloud glossary, providing separate explanations for TiDB Serverless ({{{ .starter }}}) and for TiDB Cloud Dedicated/Self-Managed clusters. The change improves clarity by distinguishing between RU as a billing metric and as a resource management unit. I have one minor suggestion to correct a grammatical error for better readability.

[ti-chi-bot]

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[ti-chi-bot]

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[nicole-yc]

LGTM