feat: add sequential fit tools

[ycexiao]

Problem

Add tools for sequential fit.

Input: input_data_folder_path, structure_file_path, output_folder_path
Output: result JSON files in the output folder.

When specified, also plot variables such as the lattice parameter, results such as the current PDF, and analyses such as the residuals during the fit.

Proposed solution

• Refactor PDFAdapter to get a modular interface
• Implement SequentialPDFFitRunner

Names are tentative.

[ycexiao]

It is completed by #16, #17, #18, and #20