feat: impl __field__ special matcher to project value columns

[waynexia]

I hereby agree to the terms of the GreptimeDB CLA

What's changed and what's your intention?

Implement __field__ special matcher. It can do projection on value columns under multi-value model. E.g.:

MySQL [(none)]> TQL eval (1667446797, 1667446807, '10s') system_metrics{ __field__="cpu_util"};
+----------+-------+-------+---------------------+
| cpu_util | host  | idc   | ts                  |
+----------+-------+-------+---------------------+
|     11.8 | host1 | idc_a | 2022-11-03 03:40:07 |
|       50 | host1 | idc_b | 2022-11-03 03:40:07 |
|     80.1 | host2 | idc_a | 2022-11-03 03:40:07 |
+----------+-------+-------+---------------------+
3 rows in set (0.005 sec)

MySQL [(none)]> TQL eval (1667446797, 1667446807, '10s') system_metrics{ __field__="cpu_util", __value__="disk_util"};
+-----------+----------+-------+-------+---------------------+
| disk_util | cpu_util | host  | idc   | ts                  |
+-----------+----------+-------+-------+---------------------+
|      10.3 |     11.8 | host1 | idc_a | 2022-11-03 03:40:07 |
|      40.6 |       50 | host1 | idc_b | 2022-11-03 03:40:07 |
|        90 |     80.1 | host2 | idc_a | 2022-11-03 03:40:07 |
+-----------+----------+-------+-------+---------------------+
3 rows in set (0.004 sec)

MySQL [(none)]> TQL eval (1667446797, 1667446807, '10s') system_metrics{ __field__!="cpu_util"};
+-----------+-------------+-------+-------+---------------------+
| disk_util | memory_util | host  | idc   | ts                  |
+-----------+-------------+-------+-------+---------------------+
|      10.3 |        10.3 | host1 | idc_a | 2022-11-03 03:40:07 |
|      40.6 |        66.7 | host1 | idc_b | 2022-11-03 03:40:07 |
|        90 |        70.3 | host2 | idc_a | 2022-11-03 03:40:07 |
+-----------+-------------+-------+-------+---------------------+
3 rows in set (0.005 sec)

Checklist

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.

Refer to a related PR or issue link (optional)

[codecov]

Codecov Report

Merging #1320 (6405a45) into develop (2458b4e) will decrease coverage by 0.40%.
The diff coverage is 99.47%.

❗ Current head 6405a45 differs from pull request most recent head 5921067. Consider uploading reports for the commit 5921067 to get more accurate results

@@             Coverage Diff             @@
##           develop    #1320      +/-   ##
===========================================
- Coverage    85.82%   85.43%   -0.40%     
===========================================
  Files          504      505       +1     
  Lines        76288    76687     +399     
===========================================
+ Hits         65473    65515      +42     
- Misses       10815    11172     +357     

[killme2008]

@waynexia The PR content must be edited too. The __value__ is renamed to __field__.

[killme2008]

LGTM