What (a) total number of social housing projects and/or schemes have been built in each municipality in Gauteng (i) in the past five financial years and (ii) since 1 April 2020, (b)(i) number of the housing projects were (aa) completed and (bb) occupied and (ii) on what date was each housing project completed and occupied, (c) procedure and/or mechanism was used to source the deserving beneficiaries and (d) are the key common challenges that are usually experienced in the process of identifying and selecting beneficiaries?