Indent names of nested sections

Indent section names in Catch2 output by their level of nesting.

ie.
```
Test Case
Section
Nested Section
Further Nested Section
```
Should become
```
Test Case
Section
Nested Section
Further Nested Section
```

Start by locating Catch2’s output formatting for nested section names. Compare the current output with the requested nesting levels in the issue, then verify the resulting output against those examples and add coverage if the relevant output tests are found.

Written by the indexing model from the issue text.