KTNB-284 Add support for passing in-memory values as display data or execution results

[cmelchior]

This PR is the kernel part of https://youtrack.jetbrains.com/issue/KTNB-284

This PR extends the Jupyter messages being sent from the Server to the Client with a new inMemoryResult. This field only makes sense for the embedded kernel used in IntelliJ, as it contains the display result as a pure in-memory object rather than serializing it to JSON.

In-memory results are represented using the InMemoryMimeTypedResult display result. This type also contains fallback data that will be used by the front-end when the in-memory result isn't available, like when saving a file to disk. Currently, the fallback data is a screenshot of the UI.

In terms of public user facing API's. This PR also introduces a new helper method called SWING() which can be used in combination with the DISPLAY helper function.

Usages:

// Cell 1: 
import java.awt.Color
import java.awt.Dimension
import java.io.File
import javax.swing.JButton
import javax.swing.JFrame
import javax.swing.JPanel

val frame = JFrame("Color Changer")
frame.defaultCloseOperation = JFrame.EXIT_ON_CLOSE
frame.preferredSize = Dimension(300, 200)
val panel = JPanel()
panel.preferredSize = Dimension(300, 200)
val button1 = JButton("Button 1")
val button2 = JButton("Button 2")
val button3 = JButton("Button 3")
button1.addActionListener { panel.background = Color.RED }
button2.addActionListener { panel.background = Color.GREEN }
button3.addActionListener { panel.background = Color.BLUE }
panel.add(button1)
panel.add(button2)
panel.add(button3)
frame.add(panel)
frame.pack()
panel

// Output1: 
<panel> will be rendered

// Cell2:
SWING(panel)

// Output2: 
<panel> will be rendered, similar to output1

// Cell3:
DISPLAY(SWING(panel))

// Output3: 
<panel> will be rendered, similar to output1, but multiple DISPLAY results can be sent.

TODO:

• [ ] Review the architecture for sending events this way.
• [ ] Review the mimetype-definitions. Should we do it differently?
• [ ] Add better tests. Currently testing as been done by-hand.
• [ ] Should we bump the kernel version?

[cmelchior]

Moving review to Space