Add show/hide log level button (Airflow UI)

### Description

Right now when we want to copy logs from the task instance we should remove some additional log parts like "INFO - " or timestamp. For timestamp there's a button to hide it. I suggest to add the similar button for hiding log level.

### Use case/motivation

It will allow users to copy-paste log information without additional formating. They will see the same log as they would see it locally.

### Related issues

_No response_

### Are you willing to submit a PR?

- [x] Yes I am willing to submit a PR!

### Code of Conduct

- [x] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

Start by locating the Airflow UI task-instance log viewer and the existing timestamp visibility control. Add a corresponding show/hide log-level control, and verify that toggling it changes whether prefixes such as "INFO - " appear when viewing or copying logs.

Written by the indexing model from the issue text.