Add People/Performance_Points_Maintainers page with adjustments to People/Performance_Points_Committee

[tsunyoku]

• Adds a page for performance points maintainers
• Makes adjustments to performance points committee page to better reflect workflow
• Moves recently retired performance points committee members to previous members

[Walavouchey]

i question the need for this new article. it's just 2 people that are already in the pp committee

if you want to document the group that can merge into pp-dev, you can add that as a new section in the pp committee article, mirroring how ppy/news-approval is a separate section in the wiki maintainer list