Add PlatformAndReleaseDateFilterProvider to enhance experimentation f…

[isidorn]

PR by me and Copilot (Opus)

I did not test this out. But happy to do that if the approach looks reasonable

fixes https://github.com/microsoft/vscode-internalbacklog/issues/6397

[Copilot]

Pull request overview

This PR adds a new PlatformAndReleaseDateFilterProvider to enhance the experimentation service with platform and VS Code release date information. The provider reads VS Code's product.json file to extract the release date and combines it with platform information to create experimentation filters that can be used for A/B testing and feature rollouts.

Key changes:

• Adds PlatformAndReleaseDateFilterProvider class that implements IExperimentationFilterProvider
• Extracts platform information using existing PlatformToString utility
• Parses release date from VS Code's product.json file in ISO format and converts it to YYYYMMDDHH format
• Registers the new filter provider in MicrosoftExperimentationService constructor

[Copilot]

The _initReleaseDate method is called asynchronously in the constructor but not awaited, creating a race condition. If getFilters() is called before the file read completes, _releaseDate will be undefined and the release date filter will not be set on the first call(s).

Since IExperimentationFilterProvider.getFilters() is synchronous, consider one of these approaches:

1. Use synchronous file reading (e.g., fs.readFileSync via a Node.js service wrapper) if this code only runs in Node.js environment
2. Read the file eagerly during service initialization and pass the value to the constructor
3. Accept that the filter might be missing initially and document this behavior