[Feature Request] Support showing timestamp in debug log

**Related command**
`--debug`

**Is your feature request related to a problem? Please describe.**
Currently, no timestamp is shown in the debug log. It is ok for GitHub Actions and Azure DevOps has they have their built-in timestamp for each line of output, but when an Azure CLI command is run locally, there is no timestamp in the debug log.

Timestamps can be helpful in troubleshooting long delays or profiling commands' performance.

**Describe the solution you'd like**
Add a config such as `core.debug_show_timestamp` to control whether timestamp is shown in the debug log.

**Describe alternatives you've considered**
Do this without a config, but only with an environment variable, such as `AZURE_DEBUG_SHOW_TIMESTAMP`.

**Additional context**