tiflash replica synchronization progress monitoring

[glkappe]

Feature Request

Is your feature request related to a problem? Please describe:

Describe the feature you'd like:

need

1. Table-level tiflash replica synchronization progress
2. Sync progress of all tiflash copies
3. The progress needs to be quasi-real-time
4. Display can be monitoring or tables

Describe alternatives you've considered:

Teachability, Documentation, Adoption, Migration Strategy:

[hehechen]

progress in information_schema.tiflash_replica can show the sync progress of all tiflash copies in quasi-real-time now.