Startup stalls and Python environments appear missing during activation

[eleanorjboyd]

Problem

When VS Code opens a Python workspace, the extension can stall during startup and some environment managers fail to register. Users then see missing or incorrect Python environments until reload.

What users might see

• Slow startup or temporary UI freeze when opening a project
• High CPU during startup
• Environment list missing expected entries (especially non-system managers)
• Environment selection/activation not working right away
• In some cases, repeated terminal/process churn

How it arises

• On activation, multiple managers register in parallel.
• Some managers fall back to PET-based detection during registration.
• If PET is still cold/initializing (common on slower, remote, or containerized setups), requests can timeout.
• Timeout/retry behavior can cascade, leaving managers unregistered for that session.

Steps to reproduce

• Open a Python project in a fresh VS Code session.
• Use a machine/workspace with slower startup conditions (remote, container, or heavy load).
• Wait for Python Environments extension activation.
• Open the environment picker/tree.
• Observe startup delay and potentially missing managers/environments.
• Expected behavior
• Startup remains responsive and manager registration does not block or fail; environments appear reliably.

Actual behavior

• Startup can hang briefly, and some managers/environments are unavailable until another refresh or reload.

[eleanorjboyd]

through detailed investigation, my hypothesis is that this PR will fix it. #1423 or at least dramatically improve results. Will watch for user input on if this change leads to improvement