*: add START_TIME and UPTIME columns to system table CLUSTER_INFO

[lonng]

What problem does this PR solve?

This PR resolves issues #14707

What is changed and how it works?

1. Report the start timestamp of TiKV to PD (server: report the start timestamp of current node to PD tikv/tikv#6581).
2. Save TiKV start timestamp in PD and provide an HTTP API to retrieve the start timestamp of TiKV and PD (server: add start_timestamp for cluster components tikv/pd#2116).
3. Add two columns (START_TIME and UPTIME) to the system table information_schema.cluster_info

Check List

Tests

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

mysql> select * from cluster_info;
+------+-----------------+-----------------+----------------------------------------------+------------------------------------------+---------------------------+-----------------+
| TYPE | INSTANCE        | STATUS_ADDRESS  | VERSION                                      | GIT_HASH                                 | START_TIME                | UPTIME          |
+------+-----------------+-----------------+----------------------------------------------+------------------------------------------+---------------------------+-----------------+
| tidb | 0.0.0.0:49920   | 0.0.0.0:12080   | 5.7.25-TiDB-v4.0.0-beta-100-g75bfcb6c5-dirty | 75bfcb6c5ddeac8f0d0a083929f306001ce69b5f | 2020-02-11T07:57:04+08:00 | 1m15.941958783s |
| tidb | 0.0.0.0:49900   | 0.0.0.0:10080   | 5.7.25-TiDB-v4.0.0-beta-100-g75bfcb6c5-dirty | 75bfcb6c5ddeac8f0d0a083929f306001ce69b5f | 2020-02-11T07:56:32+08:00 | 1m47.941966943s |
| pd   | 127.0.0.1:49901 | 127.0.0.1:49901 | 4.0.0-alpha                                  | d1cf01e084d40b7a07aa9a7c9890175a97815448 | 2020-02-11T07:56:27+08:00 | 1m52.94196873s  |
| tikv | 127.0.0.1:49903 | 127.0.0.1:49904 | 4.0.0-alpha                                  | 8af4016554b05de9334b1b821145fa92941b660d | 2020-02-11T07:56:37+08:00 | 1m42.941970325s |
+------+-----------------+-----------------+----------------------------------------------+------------------------------------------+---------------------------+-----------------+
4 rows in set (0.09 sec)

Release note

• Add two columns (START_TIME and UPTIME) to the system table information_schema.cluster_info

[crazycs520]

LGTM

[wjhuang2016]

LGTM

[lonng]

/merge

[sre-bot]

/run-all-tests

[sre-bot]

@lonng merge failed.

[lonng]

/merge

[sre-bot]

/run-all-tests