Results from spike #20492. Issues to tackle next to start using environment variables for activation:

• Allow specifying workspace-specific EnvironmentVariableCollection mutators vscode#171173
• Allow specifying prompt prefix via Environment variable collection vscode#188969
• EnvironmentVariableCollection.description only works for one extension vscode#186859
• EnvironmentVariableCollection.description is not shown in the hover when the environment is stale vscode#186798
• Allow to provide description to environment collection API vscode#171108
• env set in my fish config prevails over what I set in the env var collection vscode#184009
• Prepending fails on zsh with only shell integration enabled vscode#188875
• Add isProposedApiEnabled check for env var scope vscode#182966
• Revert change to always update status vscode#181755
• https://github.com/microsoft/vscode-internalbacklog/issues/3801
• Description is not changing for terminals which are not interacted with vscode#180851
• Allow EnvironmentVariableCollection API to apply changes via shell integration vscode#179476
• Ensure we use correct workspace folder for remote terminals vscode#180486
• Improve terminal action hover UI vscode#180739
• Allow an extension to control a terminal tab title/description variable vscode#171175
• Surface environment variable information in hover, even when not stale vscode#177078
• Add terminal tab hover action to show environment variable contributions vscode#177128
• EnvironmentVariableCollection API enhancements vscode#182069

Once these are done, implement using them in the Python extension:

• Support pythonTerminalEnvVarActivation experiment in multiroot workspaces #21101
• Set environment variables as part of shell integration using VSCode API #21297
• Prompt does not show up for terminal activation #20827
• Show notification reaffirming Python extension still handles activation even if no prompt is shown #21793