use posit cdn instead of github release asset for download url

[sharon-wang]

We no longer publish the release binaries as assets, but the downloadAndUnzipPositron() function still assumes that we do.

This PR updates the script to use the CDN url so we shouldn't see this error anymore when running Python extension MacOS tests:

Run GabrielBB/xvfb-action@v1.7
/Users/runner/hostedtoolcache/node/20.12.1/arm64/bin/npm run testDebugger

> python@2025.99.0-dev testDebugger
> node ./out/test/testBootstrap.js ./out/test/debuggerTest.js

Test server listening on port 49253
****************************************************************************************************
Start Debugger tests
Using Github PAT from environment variable POSITRON_GITHUB_PAT.
End Debugger tests (with errors) Error: No asset found with suffix .dmg for platform darwin
    at downloadAndUnzipPositron (/Users/runner/work/positron/positron/path with spaces/extensions/positron-python/out/test/positron/testElectron.js:197:15)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async runTests (/Users/runner/work/positron/positron/path with spaces/extensions/positron-python/out/test/positron/testElectron.js:269:63)
Exiting with test failures
Killing VSC
Error: The process '/Users/runner/hostedtoolcache/node/20.12.1/arm64/bin/npm' failed with exit code 1

QA Notes

Python Mac OS tests should now pass locally and in CI.

[github-actions]

E2E Tests 🚀
This PR will run tests tagged with: @:critical

^{readme  valid tags}

[sharon-wang]

Removed this as it doesn't seem like we support linux/win32 anyways? See lower down in this function where we look for the executablePath -- only mac is supported there.

[sharon-wang]

This is where the error was occurring. We no longer publish assets for the binaries.

[timtmok]

@petetronic Should we add something to the download URL to exclude this from download reporting? This is going to download a prerelease Positron on every PR. I'm not even sure why we need to download it for a PR test.

[petetronic]

@petetronic Should we add something to the download URL to exclude this from download reporting? This is going to download a prerelease Positron on every PR. I'm not even sure why we need to download it for a PR test.

Good point, if we can set a user agent, or if not, a query param, that marks it as Positron CI, that would be useful.