insights: correct over-reporting / aggregation of data points

[emidoots]

Fixes #18582

Signed-off-by: Stephen Gutekanst stephen@sourcegraph.com

[sourcegraph-bot]

Notifying subscribers in CODENOTIFY files for diff aaee832...9f84424.

Notify	File(s)
@felixfbecker	enterprise/internal/insights/store/store.go enterprise/internal/insights/store/store_test.go

[emidoots]

Also confirmed with the data on Sourcegraph.com that the currently non-sensical chart for fmt.Errorf and fmt.Printf search results:

Is sane afterwards:

      time_bucket       |   sum   |                             series_id                              | metadata 
------------------------+---------+--------------------------------------------------------------------+----------
 2021-02-24 12:00:00+00 | 2801920 | s:087855E6A24440837303FD8A252E9893E8ABDFECA55B61AC83DA1B521906626E | 
 2021-02-24 00:00:00+00 | 2800148 | s:087855E6A24440837303FD8A252E9893E8ABDFECA55B61AC83DA1B521906626E | 
 2021-02-23 12:00:00+00 | 2799886 | s:087855E6A24440837303FD8A252E9893E8ABDFECA55B61AC83DA1B521906626E | 
 2021-02-23 00:00:00+00 | 2799837 | s:087855E6A24440837303FD8A252E9893E8ABDFECA55B61AC83DA1B521906626E | 
 2021-02-22 12:00:00+00 | 2799512 | s:087855E6A24440837303FD8A252E9893E8ABDFECA55B61AC83DA1B521906626E | 
 2021-02-22 00:00:00+00 | 2799219 | s:087855E6A24440837303FD8A252E9893E8ABDFECA55B61AC83DA1B521906626E | 
(6 rows)


      time_bucket       |   sum   |                             series_id                              | metadata 
------------------------+---------+--------------------------------------------------------------------+----------
 2021-02-24 12:00:00+00 |  118923 | s:7FBD292BF97936C4B6397688CFFB05DEA95E650C3D5B653AAEA8F77BBD25CE93 | 
 2021-02-24 00:00:00+00 |  118902 | s:7FBD292BF97936C4B6397688CFFB05DEA95E650C3D5B653AAEA8F77BBD25CE93 | 
 2021-02-23 12:00:00+00 |  118893 | s:7FBD292BF97936C4B6397688CFFB05DEA95E650C3D5B653AAEA8F77BBD25CE93 | 
 2021-02-23 00:00:00+00 |  118893 | s:7FBD292BF97936C4B6397688CFFB05DEA95E650C3D5B653AAEA8F77BBD25CE93 | 
 2021-02-22 12:00:00+00 |  118909 | s:7FBD292BF97936C4B6397688CFFB05DEA95E650C3D5B653AAEA8F77BBD25CE93 | 
 2021-02-22 00:00:00+00 |  118905 | s:7FBD292BF97936C4B6397688CFFB05DEA95E650C3D5B653AAEA8F77BBD25CE93 | 
(6 rows)