Migration to no login/whitelist

[abe33]

This is an issue just to keep track of the things in the installer that will be affected by the login and whitelist removal.

A quick reminder first, unlike Atom, VSCode install flow setup and views are largely done in the plugin itself.

• Do we want to keep all the account steps in the first place? I feel this could be removed entirely to let the copilot handle that and make the install flow just a download and install task.
• If not, is the authenticate step still relevant? I think here, the now removed authenticateSessionID should be brought back in the step object if we want to keep that step. That function was only used here so it's more relevant to have it in the step rather than exposed by the API.
• Whitelist steps are only a thing in VScode, it still runs an old version of the kite-installer before we removed these steps.
• The whole vscode install flow should be reworked. But this should be done only after merging Switch to webview api vscode-plugin#174 (switch to webview API)