Kernel creation feels slower

[rebornix]

    My impression of the slowness that @DonJayamanne mentioned

In stable and insiders, I think the run button shows up at about the same time. Around 7-9s from "reload window" to the run button appearing, hard to tell whether stable is slightly faster.

But after it appears, and the preferred kernel has been discovered, I see "Discovering Kernels" for another 5s or more, which could lead to an impression of slowness if the user doesn't realize they can go ahead and run a cell at this point.

Originally posted by @roblourens in microsoft/vscode-jupyter#11963 (comment)

[rebornix]

When there is already a selected kernel, we should show the kernel name and a spinner if there are pending detection tasks.