Dynamic BDD-style macros

**Description**
`DYNAMIC_SECTION` makes it easy to generate portions of test cases. However, when used inside a BDD scenario, it results in unsightly output when a test fails:

```
Scenario: move_up() returns true if cursor position changed
Given: a ListWidget with 3 lines
cursor on position 2
moving up and wrap_scroll is false
Then: true is returned and cursor moves to position 1
```

As you can see, a couple lines weren't prefixed with BDD terms.

It would be nice to have `DYNAMIC_` counterparts to all the BDD macros, so the output looked like this:

```
Scenario: move_up() returns true if cursor position changed
Given: a ListWidget with 3 lines
And given: cursor on position 2
When: moving up and wrap_scroll is false
Then: true is returned and cursor moves to position 1
```

**Additional context**
Add any other context or screenshots about the feature request here.