[lldb] Reland: Add Pythonic API to SBStructuredData extension (#156771)
* Adds `dynamic` property to automatically convert `SBStructuredData`
instances to the associated Python type (`str`, `int`, `float`, `bool`,
`NoneType`, etc)
* Implements `__getitem__` for Pythonic array and dictionary
subscripting
* Subscripting return the result of the `dynamic` property
* Updates `__iter__` to support dictionary instances (supporting `for`
loops)
* Adds `__str__`, `__int__`, and `__float__`
With these changes, these two expressions are equal:
```py
data["name"] == data.GetValueForKey("name").GetStringValue(1024)
```
**Note**: Unlike the original commit (#155061), this re-commit removes
the `__bool__` implementation, which broke crashlog. Somewhere in the
crashlog execution, it depends on `__bool__` meaning only `IsValid()`.
Additionally did some cleanup in TestStructuredDataAPI.py.