Clean context paths handling

The usage of context_root_dir was misleading as it was actually holding the data_dir. This MR removes all occurrences of context_root_dir, simply replacing it with data_dir .

In addition to that, the usage of context_path in the baker(*) was misleading as well. This MR changes it to make the use of data_dir as well.

Manually testing the MR

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR