Add: Accessibility Panel - Notehead Scheme option

[nasehim7]

Hi All, This is the PR related to GSoC '24 - Accessibility Profiles project. To check what is goal for this project, kindly refer to: https://musescore.org/en/user/1088561/blog/2024/05/27/gsoc-2024-project-accessibility-profiles-musescore

Current Status of the PR:

UI Changes:

• [x] Add Notehead Scheme dropdown

Backend Changes:

• [x] Add Notehead Scheme dropdown backend code. (WIP)

Open Issues: None

Enhancements: None

• [x] I signed the CLA
• [x] The title of the PR describes the problem it addresses
• [x] Each commit's message describes its purpose and effects, and references the issue it resolves
• [x] If changes are extensive, there is a sequence of easily reviewable commits
• [x] The code in the PR follows the coding rules
• [x] There are no unnecessary changes
• [x] The code compiles and runs on my machine, preferably after each commit individually
• [x] I created a unit test or vtest to verify the changes I made (if applicable)