Reduce the number of startup notifications

[brettcannon]

No description provided.

[DonJayamanne]

• We might want to consider waiting till VS Code comes up with a new UX for notifications/startup messages.
• Also, we could defer loading (executing) parts of the extension until the extension has been configured (e.g. an interpreter has been selected).
  • Discussed with @karthiknadig about this.

[luabud]

These are/were the main notifications that show(ed) on load and their current status:

Notification	Status	More Info
"pylint is not installed"	🚮	The notification will only show for workspaces who have pylint explicitly configured in their settings. Doesn't show for new/blank workspaces anymore
"You need to select an interpreter to use the Python extension features" notification	🚮	The notification doesn't show up on load anymore. Only when users trigger something that requires an interpreter to be selected.
"Join our insiders program" notification (when using VS Code Insiders only)	🚮	Notification is no longer displayed since we moved to pre-release
"The default macOS interpreter isn't optimal to be used by the Python extension" notification	🚮	Not displayed on load anymore
"Python is not installed" notification	✋	This notification is still displayed on load but only for users who don't have Python installed. We plan to remove it by addressing #19099
"Tip: you can select the interpreter through the status bar"	🚮	This notification was removed entirely
"Update inheritEnv setting when using conda"	✋	This notification is still being displayed, we still need a good solution for it to be removed (#19001)

[luabud]

Closing in favour of #19174