[OptTable] Make new lines in help text respect indentation (#75366)

With this changes, new lines in the HelpText defined in OptTable have
the same indentation as the first line.

Before, the help output will look something like:

```
--color=<value>       Whether to use color when
symbolizing log markup: always, auto, never
```

With this change:

```
--color=<value>       Whether to use color when
                      symbolizing log markup: always, auto, never
```