Create new command to interpolate text into code, to run in the console

In https://github.com/posit-dev/positron/discussions/5747 we've got a feature request for a command similar to workbench.action.executeCode.console that would allow someone to interpolate a selection into a bit of code, to run in the console. Something like this:

{
    "key": "Cmd+Shift+S",
    "command": "workbench.action.executeSelection.console",
    "when": "editorTextFocus",
    "args": {
        "langId": "r",
        "code": "str(${selectedText})",
        "focus": true
    }
}

You can already run selected code, but this is about selecting code and then constructing/interpolating a new bit of code to run.

Start by comparing the requested command with workbench.action.executeCode.console and reviewing discussion 5747. Trace how the example's selectedText, langId, code, and focus arguments should be handled. Done means a command like workbench.action.executeSelection.console can interpolate the selection into code and run it in the console.