infoschema,store: fix the inconsistent definition of StoreStatus between TiDB/PD (#11969)

[sre-bot]

cherry-pick #11969 to release-3.0

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Signed-off-by: Lonng heng@lonng.org

What problem does this PR solve?

Protocol incompatible with PD-Server, introduced in #10248.
Fix #11960, #11294

What is changed and how it works?

This PR change the type of RegionScore and RegionWeight to float64.
See: https://github.com/pingcap/pd/blob/561d00414f9e43b3ba6da9a34d82c6d7acd16ae2/server/api/store.go#L42

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

  mysql> select * from INFORMATION_SCHEMA.TIKV_STORE_STATUS\G
  *************************** 1. row ***************************
          STORE_ID: 1
          ADDRESS: 127.0.0.1:20160
      STORE_STATE: 0
  STORE_STATE_NAME: Up
              LABEL: null
          VERSION: 4.0.0-alpha
          CAPACITY: 466 GiB
          AVAILABLE: 199 GiB
      LEADER_COUNT: 20
      LEADER_WEIGHT: 1
      LEADER_SCORE: 20
      LEADER_SIZE: 20
      REGION_COUNT: 20
      REGION_WEIGHT: 1
      REGION_SCORE: 20
      REGION_SIZE: 20
          START_TS: 2019-09-02 10:42:29
  LAST_HEARTBEAT_TS: 2019-09-02 10:43:29
          UPTIME: 1m0.808967s
  1 row in set (0.00 sec)
  

Code changes

• Has exported function/method change

Related changes

• Need to cherry-pick to the release branch

Release note

• Fix the inconsistent definition of StoreStatus between TiDB/PD

[sre-bot]

/run-all-tests

[winkyao]

LGTM

[AilinKid]

LGTM