Implement access specifier folding range collection and add unit tests

[Prashant Kumar Rai (8prashant)]

Adds folding ranges for class access specifier sections (public:, private:, protected:) so users can collapse each section independently.

Related to #14645.

What changed

• Added access-specifier folding detection logic in a pure utility module.
• Integrated those computed ranges into the existing folding range provider response.
• Kept existing server-provided folding behavior and appended the new client-side ranges.

Why

When classes contain multiple access blocks, collapsing by section helps reduce noise and improves readability, especially in large third-party headers.

Testing

• Built extension successfully:
  • yarn compile
• Ran targeted unit test successfully:
  • mocha dist/test/unit/foldingRangeProvider.test.js --timeout 30000
• Result:
  • 1 passing, 0 failing

[Prashant Kumar Rai (8prashant)]

@microsoft-github-policy-service agree

[Copilot]

Pull request overview

Adds collapsible folding ranges for C++ class access-specifier sections while retaining server-provided ranges.

Changes:

• Implements client-side access-section detection.
• Integrates detected ranges with server results.
• Adds a basic unit test.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
foldingRangeUtils.ts	Detects access-specifier folding ranges.
foldingRangeProvider.ts	Appends client-computed ranges.
foldingRangeProvider.test.ts	Tests basic access-section folding.

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[Prashant Kumar Rai (8prashant)]

Hi Sean McManus (@sean-mcmanus), I’ve addressed the comments from the previous review and made the requested changes in the latest commit. Could you please revalidate the CI and Copilot validation when you get a chance? Thanks!

[Colen Garoutte-Carson (Colengms)]

Hi Prashant Kumar Rai (@8prashant) . Thanks again for another great contribution. (We do appreciate it! I've wanted this feature myself, for a while now.) Though, in this case, the right place for this logic is actually in a native/closed-source component, shared with Visual Studio. I've gone ahead and composed an alternative implementation (which would also add the feature to VS), which is now in PR internally. I don't believe we'll want to adopt this TypeScript-based approach.