Features: Clean up use of "get_common_setting"

[samruddhikhandale]

Status of https://github.com/search?q=repo%3Adevcontainers%2Ffeatures%20get_common_setting&type=code

Some of the Features are fetching properties from https://aka.ms/vscode-dev-containers/script-library/settings.env which is hosted in the microsoft/vscode-dev-container repos

We should stop using that file, and directly add properties to the Features