Fix telemetry bundling issues

[bwateratmsft]

Fixes #6697

TODO:

• Verify telemetry is being uploaded

[Copilot]

Pull request overview

This PR updates the VS Code extension’s engineering/telemetry and linting setup so that telemetry bundling works correctly with the newer azext engineering package and extension telemetry pipeline.

Changes:

• Bump @microsoft/vscode-azext-eng and related dev/test dependencies in ext/vscode/package.json, and align ext/vscode/package-lock.json with updated telemetry and tooling libraries (e.g., @vscode/extension-telemetry 1.4.0 and newer Application Insights/1DS packages).
• Replace the simple re-export of the azext ESLint config with a flat-config eslint.config.mjs that wraps azExtEslintRecommendedTypeChecked and adds a header/header rule to enforce the standard Microsoft copyright header with trailing empty lines.
• Minor whitespace cleanup in authServer.ts (no functional impact).

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated no comments.

File	Description
ext/vscode/src/utils/authServer.ts	Removes stray leading whitespace before the file header comment; no behavioral changes.
ext/vscode/package.json	Updates dev dependencies (@microsoft/vscode-azext-eng, sinon, @types/sinon) to newer versions to pick up the fixed telemetry pipeline and newer test tooling.
ext/vscode/package-lock.json	Synchronizes the lockfile with the updated dev and runtime dependencies, including telemetry-related libraries and ESLint/tooling ecosystem packages.
ext/vscode/eslint.config.mjs	Switches to ESLint flat config via defineConfig, layering the azext recommended type-checked config with a custom header/header rule enforcing the standard Microsoft copyright and license header format.

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[azure-sdk]

VSCode Extension Installation Instructions

1. Download the extension at https://azuresdkartifacts.z5.web.core.windows.net/azd/vscode/pr/6698/azure-dev-0.11.0-alpha.1.vsix
2. Extract the extension from the compressed file
3. In vscode
   a. Open "Extensions" (Ctrl+Shift+X)
   b. Click the ...\ menu at top of Extensions sidebar
   c. Click "Install from VSIX"
   d. Select location of downloaded file