[Hammer Editor] Object Properties - Implement "Copy Keys" and "Paste Keys"

[LiminalCrab]

For?

Hammer

What can't you do?

When attempting to copy the keys from your object properties window, "(TODO: Hammer clipboard data on the system clipboad.)" is copied instead.

Implementing this would give us a quick and easy way to not only share our entities with one another in a quick copy and paste, but make it easier to quickly look through and adjust the settings in a notepad if need be.

How would you like it to work?

I would like to click "Copy Keys" and have it copy all of the keys and their set values to my clipboard. I would like to click "Paste keys" in the Object Properties and have it paste the content of my "Copied keys" into the Object Properties.

What have you tried?

You can copy them individually at the moment, though the naming is off a bit. I honestly wouldn't mind it stuck like this for now so long as we just had it implemented.

This is Quadratic Attenuation
{
    attenuation2 = "0"
}

This is Linear:

{
    attenuation1 = "1"
}

Additional context

No response

[robotboy655]

Related: https://github.com/sboxgame/issues/issues/2815

[LiminalCrab]

You can shift select and copy

{ cubemapfogheightstart = "2000.0" cubemapfogheightwidth = "0.0" cubemapfogfalloffexponent = "2.0" cubemapfogenddistance = "6000.0" cubemapfogstartdistance = "0.0" cubemapfogheightexponent = "2.0" }