lightning: precheck doesn't check local disk resources and cluster available

[sleepymole]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

Use a single lightning to import data.

2. What did you expect to see? (Required)

+----+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+
|  # | CHECK ITEM                                                                                                                         | TYPE        | PASSED |
+----+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+
|  1 | Source csv files size is proper                                                                                                    | performance | true   |
+----+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+
|  2 | checkpoints are valid                                                                                                              | critical    | true   |
+----+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+
|  3 | table schemas are valid                                                                                                            | critical    | true   |
+----+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+
|  4 | Cluster is available                                                                                                               | critical    | true   |
+----+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+
|  5 | Lightning has the correct storage permission                                                                                       | critical    | true   |
+----+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+
|  6 | sorted-kv-dir:sorted-kv-dir and data-source-dir:/home/xyj/Projects/tidb/.dev/test-data4 are in the same disk, may slow down perfor | performance | false  |
|    | mance                                                                                                                              |             |        |
+----+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+
|  7 | local disk resources are rich, estimate sorted data size 851.6MiB, local available is 33.04GiB                                     | critical    | true   |
+----+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+
|  8 | Cluster available is rich, available is 33.04GiB, we need 2.495GiB                                                                 | critical    | true   |
+----+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+
|  9 | Cluster doesn't have too many empty regions                                                                                        | critical    | true   |
+----+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+
| 10 | Cluster region distribution is balanced                                                                                            | critical    | true   |
+----+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+

3. What did you see instead (Required)

+---+----------------------------------------------+-------------+--------+
| # | CHECK ITEM                                   | TYPE        | PASSED |
+---+----------------------------------------------+-------------+--------+
| 1 | Source csv files size is proper              | performance | true   |
+---+----------------------------------------------+-------------+--------+
| 2 | checkpoints are valid                        | critical    | true   |
+---+----------------------------------------------+-------------+--------+
| 3 | table schemas are valid                      | critical    | true   |
+---+----------------------------------------------+-------------+--------+
| 4 | Cluster is available                         | critical    | true   |
+---+----------------------------------------------+-------------+--------+
| 5 | Lightning has the correct storage permission | critical    | true   |
+---+----------------------------------------------+-------------+--------+

4. What is your TiDB-Lightning version? (Required)

master