[Flags tab] Table improvements

[aj-codecov]

codecov/feedback#27 three of four users asked for this to see WHERE data is coming from for each flag - likely time/date of upload and link to commit is necessary - specific comment: codecov/feedback#27 (comment)

[aj-codecov]

from benoss:
I would really like to have:

• Branch context dropdown
• Last report uploaded time column (and be able to filter/order by this column so that we can check if CI/CD is uploading correctly the flag data)
• Order by Coverage% / Filter by more than/less than % (Find the flags under the baseline that we need to focus on)
• Order by Trend%/ Filter by more than/less than % (Find the flags that are not going well)
• Click on the flag to have a flag detail page with more info about this flag