virtualbox features

_This issue was originally opened by @gamethis as hashicorp/packer#9312. It was migrated here as a result of the [Packer plugin split](https://github.com/hashicorp/packer/issues/8610#issuecomment-770034737). The original body of the issue is below._

#### Feature Description

I would like to see 3 items added to the virtualbox builder.
All of this can technically be done with the vboxmanage feature but would be nice so I don't constantly have to look up teh docs for what the strings are.

1. vram amount of video ram for vm. usefull for my boxes that need more than the defaults.
2. clipboard so I can enable or disable copy items between host and vm
2. copypaste so I can enable or disable copy text between vm and host.

#### Use Case(sup.)
I primarily use this for my vagrant boxes.
But would enable easy setup and transfer of items I need while cleaning up the form in packer.