Adding an app setting to allow CORS configuration

[soninaren]

resolves #8936

Host currently honors 'CORS_ALLOWED_ORIGINS' app setting only for linux consumption. Windows and linux app service go thorugh a seperate channel. However there are additional hosting scenarios that have no way of setting up CORS configuration. This change adds an app setting that allows customer to set up CORS configuration by setting "FUNCTIONS_ENABLE_CORS_CONFIGURATION" = "true"

Pull request checklist

• My changes do not require documentation changes
  • Otherwise: Documentation issue linked to PR
• My changes should not be added to the release notes for the next release
  • Otherwise: I've added my notes to release_notes.md
• My changes do not need to be backported to a previous version
  • Otherwise: Backport tracked by issue/PR #issue_or_pr
• My changes do not require diagnostic events changes
  • Otherwise: I have added/updated all related diagnostic events and their documentation (Documentation issue linked to PR)
• I have added all required tests (Unit tests, E2E tests)

Additional information

Additional PR information

[kshyju]

A few questions, otherwise LGTM.