fix: remove the broken code related to creating user snippets

The extension contained logic that enabled users to create user snippets as opposed to project-level snippets.

This MR removes the logic because:

• The feature only allowed creating user snippets in Multi-root Workspace, which means it didn't work for a vast majority of use-cases.
• The feature has been broken for months (at least two) and we didn't get a bug report
• Pasting snippets in VS Code only uses project-level snippets.

Creating snippets was completely broken in multi-repository projects, this MR fixes that

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This MR is best-reviewed commit-by-commit. Larger commits have meaningful messages

Related to #389 (closed)