Rename create_on_demand_scan policy to manage_on_demand_scan

What does this MR do?

It was suggested in 40805#note_404907037 that the :create_on_demand_scan policy authorized against more than creating an on-demand scan, but also managing DastScannerProfiles and DastSiteProfiles. Renaming to :manage_dast_scanner_profile

This MR relates to 243679

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Does this MR meet the acceptance criteria?

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