Use local checkout for fetching package.json instead of accessing github directly

[dibarbet]

Release pipeline is failing to access raw.githubusercontent.com due to network blocks when generating tags. This modifies the pipeline to use the local checkout instead (note that the pipeline checks out vscode-csharp at the commit that is being released)

[Copilot]

Pull request overview

Updates the release tagging task to avoid fetching package.json from raw.githubusercontent.com (which can be blocked in restricted networks) by reading package.json from the locally checked-out repository or via git show for the specified release commit.

Changes:

• Replaces remote fetch of package.json with local resolution via git rev-parse HEAD + git show <commit>:package.json.
• Removes the dependency on githubPAT for determining the Roslyn component commit (NuGet inspection now only needs local repo access).
• Adds small git helper utilities (getPackageJsonFromReleaseCommit, getGitOutput) to support local reads.

Show a summary per file

File	Description
tasks/tags/createTags.ts	Switches tag-generation inputs from GitHub raw content fetching to local checkout/git-object reads for package.json.

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 1

[Copilot]

Copilot's findings

• Files reviewed: 2/2 changed files
• Comments generated: 3