Add ability to group targets

[AntoineJT]

Is your feature request related to a problem? Please describe.

I'm using Visual Studio and I would like to group targets by putting them into virtual folders, to avoid my workspace being a complete mess. You can look at what Premake 5 does here: https://github.com/premake/premake-core/wiki/group

Describe the solution you'd like

I think the way Premake handles this is not the best way to do.
I think it can be better handled by doing as target does:

group("name")
    target("first_target")
        ...
    target("second_target")
        ...
group_end()

Describe alternatives you've considered

Alternatively, it may be handled like this:

target("first_target")
    ...
target("second_target")
    ...
target_end()

group("name", "first_target", "second_target")
#or
group("name", {"first_target", "second_target"})

or maybe it can be handled the same way as Premake does, but I think the better solution here for users would be the first I propose.

Additional context

Here is a preview of virtual folders in Visual Studio, using an old version of NazaraEngine that I found on my hard drive.

[AntoineJT]

Sorry for the duplicate of #1026.
I'm closing this issue and bringing my ideas to the other issue.