Pending work for basic debugging

[DavidKutu]

Work items pending from #6332

• Add context for switching kernels and notebook opened
• cache valid kernels so the button enables faster
• don't make up a random session ids
• delete temp files (the kernel is not doing this)
• use python api for checking ipykernel version
• use IDisposableRegistry
• check if we need the vscode.debug.breakpoints on activate