http: add http api for get db and table info that is related to the tableID

[crazycs520]

What problem does this PR solve?

add http api to get db and table info that is related to the tableID.
This is for the flash use.

curl http://{TiDBIP}:10080/db-table/{tableID}

This will return below now:

type dbTableInfo struct {
	DBInfo        *model.DBInfo    `json:"db_info"`
	TableInfo     *model.TableInfo `json:"table_info"`
	SchemaVersion int64            `json:"schema_version"`
}

What is changed and how it works?

Check List

Tests

Code changes

• Has exported function/method change

Side effects

Related changes

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This change is 

[crazycs520]

@zanmato1984 PTAL

[zanmato1984]

LGTM. I think you might need another approve from some TiDB team member?

[crazycs520]

@winkyao @ciscoxll PTAL

[jackysp]

I think we could get the table info by

tidb/docs/tidb_http_api.md

Line 52 in f497444

curl http://{TiDBIP}:10080/schema?table_id={tableID}

So could we append some DB info to the old API?
btw: when we get the table info, I think we could get the DB info in the other way. I'm not sure why we need to append the DB info in the same API.

[winkyao]

I think to add a new api is better, if you change the return format, will cause compatibility issues.

[crazycs520]

@winkyao PTAL

[zimulala]

LGTM

[crazycs520]

@winkyao PTAL

[winkyao]

LGTM