🎨 Improve edge cases in path handling

[elbeno]

Problem:

• Aside from literals, there isn't an easy way to make a path from a ct_string.
• root and without_root don't handle edge cases of paths being singleton/empty.
• There is no function to get the "parent" of a path.

Solution:

• Expose make_path.
• Handle edge cases in root and without_root functions.
• Add parent.

Note:

• root and without_root are primarily used in path resolution, and manipulate the topmost element.
• parent is analogous to "go up a directory" and is useful for e.g. getting a register, given a field.