Route package installs through Microsoft feed proxies

[Bill Schnurr (bschnurr)]

Summary

Port the package-feed migration from microsoft/vscode-isort#773 and microsoft/vscode-isort#775 to vscode-python-debugger.

• Route PR, push, and CodeQL package installation through Microsoft's npm and PyPI proxies.
• Remove redundant NPM_CONFIG_REGISTRY from PR/push workflows that install through npm run ci:msft; keep PIP_INDEX_URL and retain registry settings for CodeQL autobuild and Azure template consumers.
• Use npm run ci:msft in shared lint/VSIX actions and applicable test jobs, preserving package caching and the VSIX offline-cache preference.
• Route DevDiv stable/prerelease builds through the same proxies while preserving release triggers, approval gates, signing, and publishing behavior.
• Add public/Microsoft local setup commands, dependency-free regression tests, optional local lockfile-normalization hooks, and contributor documentation.

Ecosystem	Microsoft endpoint
npm	https://packagefeedproxy.microsoft.io/npm/
Python	https://packagefeedproxy.microsoft.io/pypi/simple/

Repository-specific adaptation

Root-only npm setup, with no shared-LSP dependency added. Preserve debugpy platform/wheel bundling, existing pipx/nox CI entry points, and the Actions-only Dependabot configuration.

Preserved behavior and boundaries

• Dependabot remains on public registries with its existing ecosystems, grouping, schedules, cooldowns, ignores, and limits unchanged.
• Committed lockfiles retain public npm URLs for known public-package mirrors. Local proxy rewrites are not committed.
• Dependency versions, integrity hashes, submodule revisions, and application behavior are unchanged.
• Legacy Azure stable, prerelease, and validation pipeline files are unchanged.
• Hooks are opt-in local Git hooks; GitHub and Dependabot do not execute them, and no workflow writes repair commits to PR branches.
• No changes to the shared pylance-eng templates are required.

Verification

• npm run test:setup: 39 passing tests, including Windows/Linux setup orchestration, rewrite/error handling, integrity preservation, and real temporary-repository hook tests.
• npm run lint
• npm run format-check
• npm run compile-tests
• Executable parsed-YAML comparisons against the recorded base verify proxy settings, install entry points, Python step overrides, and unchanged release gates, workflow matrices, cache settings, legacy pipelines, and Dependabot configuration.
• npm run ci:msft and standalone rewrite commands exercised locally; uncached npm and Python proxy downloads succeeded.

Hosted GitHub/Azure execution has not been claimed as verified by these local checks. This PR is intentionally a draft.