Reduce grouping in the problems panel

[aciccarello]

When I look at the problems panel, every grammerly problem is the single item in a group. This clutters the problems panel and makes it hard to read. Since the items are already grouped by file, the file name can probably be dropped from the description.

I would prefer to see items listed in the following format similar to the screenshot below:

Missing comma after introductory phrase: however [87, 507]

[znck]

Extensions cannot control how diagnostics are displayed.