Optimize Telemetry config

[HunDunDM]

Feature Request

Describe the feature you'd like:

• Rename DisableTelemetry to EnableTelemetry, consistent with TiDB. (The corresponding config of PD needs to be updated.)
• In TiDB mode, support to use SQL to obtain the telemetry status of TiDB as a serial switch.

Describe alternatives you've considered:

• Supports dynamic configuration of Telemetry. (Only when both Config.Telemetry and TiDB.Telemetry are Enable.)

Teachability, Documentation, Adoption, Migration Strategy:

Telemetry

[baurine]

In TiDB mode, support to use SQL to obtain the telemetry status of TiDB as a serial switch.

Hi @HunDunDM , what does this mean?