fix sorted column of system table

[qjiang002]

This is a sub-component of PR #518

Fix the sorted column of System table

• The sorter selector is kept separately above the table, and the sorted column in the table is fixed to the left and the column header sorter is set to be the same as the sorting direction.
• In the sorter selector, 'Created At' is changed to 'Sorted by' for easier understanding.

[lyuyangh]

Thanks! Overall, looks great!

Do you think we should also pin "Created At" if it is the sort column? Also, I agree that "Sort By" makes it clear what that selector does in the default view. But when a user wants to change the sort column from something else to "Created At" (sort by time), the label may become confusing. Now that we have moved several selectors to the table, could we maybe show "Sort By" as a prompt next to the selector but still use "Created At" as the label for that "sort by time" option?

[qjiang002]

Thanks @lyuyangh for the suggestion. I add a prefix box before the selector, and pin Created_At to the right because it is a default and less important sorted column compared with those metric columns.

[lyuyangh]

Thanks!