Command runner logging enhancements with `--debug`

One current limitation of the command runner implementation is that when running azd with `--debug`, if the command being executed takes a very long time or appears to be stuck, neither the command or output gets logged until the process exits.

-----------------------------

_Originally posted by @weikanglim in https://github.com/Azure/azure-dev/issues/5501#issuecomment-3085257044_:

Right now our command runner only logs the full output of the command after execution:

> 2025/07/17 19:22:52 command_runner.go:310: Run exec: 'git --version' , exit code: 0
-------------------------------------stdout-------------------------------------------
git version 2.45.3

A possible enhancement is to split this out into two messages:

> 2025/07/17 19:22:52 command_runner.go:310: Start: 'git --version'
> 2025/07/17 19:22:52 command_runner.go:310: Stop: 'git --version' , exit code: 0
-------------------------------------stdout-------------------------------------------
git version 2.45.3

-----------------------------

A further enhancement could be to support streaming the command output in real-time, which would make it easier to observe and debug cases like #5491, where the command being executed initiated a long-running process:

```
info: Microsoft.Hosting.Lifetime[14]
Now listening on: http://localhost:5241
info: Microsoft.Hosting.Lifetime[0]
Application started. Press Ctrl+C to shut down.
info: Microsoft.Hosting.Lifetime[0]
Hosting environment: Development
info: Microsoft.Hosting.Lifetime[0]
Content root path: /workspaces/junk_20250716/Something
```