Review silentSpinnerConsole design for extension compatibility

## Description

The deploy progress tracker wraps the console in a `silentSpinnerConsole` that no-ops `ShowSpinner`/`StopSpinner`/`IsSpinnerRunning`. This silently swallows spinner calls from any code path during deploy — including extension-defined service targets that may use spinners for their own progress.

The caller has no way to know their output was suppressed.

## Proposed Alternatives

- A console-level "table mode" that suppresses spinners by design (explicit contract)
- At minimum, log a debug message when a spinner call is dropped so extension authors can diagnose missing output
- Consider making the suppression opt-in per service target

## Context

- Requested by @vhvb1989 in [PR #7776 comment](https://github.com/Azure/azure-dev/pull/7776#issuecomment-4280643268)
- Related: #7908 (per-service output buffering)