Add option for default `log_source` setting in task logs web UI

### Description

Currently, any task log page on the web UI shows a dropdown to select the log source, with the default always being `All Sources`.

Ideally it would be great if there were an Airflow config setting like `api.default_ui_log_source`, which may optionally be set to any one of the following standard options:
* `"operator"`
* `"task"`
* `"task.stderr"`
* `"All Sources"`
* `"airflow.plugins_manager"`

If the config is not set, then the `log_source` value in the web UI defaults to the `All Sources` option as it currently does in Airflow 3.1.8.

### Use case/motivation

For many of our users, the majority of the log sources emanating from the `"All Sources"` option are irrelevant, or confusing (for example, logs from the plugin manager bootstrapping are typically not useful to many data practictioners).

Also, it is common for much of the non-task log sources to be repeated across task instances and dag runs, regardless of the task or dag in question. Again, this is particularly true for things like plugin bootstrapping.

### Related issues

Not any that I'm aware of.

### 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)