sidebar polling, workspace close, and timeouts

[siddhusaladi]

Fixes failures on macOS CI with the Previous VS Code version.

• Poll until workspace is actually closed instead of a fixed 2s sleep
• Re-fetch sidebar DOM references on every retry instead of reusing stale ones (timeout 30s → 120s)
• Isolate each LS output channel polling step so failures trigger immediate retry and dismiss notification toasts before closing the panel
• Add closeWorkspace() to LSP suite teardown so the next suite always gets a fresh open, not a 190s extension host restart
• LS init timeouts to 60s → 240s internal/300s Mocha across all LSP suites
• Explicitly restore Explorer view after the debugger test (previous VS Code doesn't do this automatically)

[siddhusaladi]

Removing failing previous VS Code version from CI pipeline for now