Add ability to set pagesize via reports_get webservice

Setup: Create a new test course size 'S' to populate the site with users Create a custom report named 'Users' using the 'Users' report source, include the default setup Verify existing functionality works: Visit the reportbuilder editor for the 'Users' report Click the 'Preview' button, verify the number of rows shown is 30 Verify new pagesize parameter works: In reportbuilder/amd/src/editor.js line 74 set the pagesize parameter to 5. .then(() => getReport(reportElement.dataset.reportId, toggledEditMode, 5 )) Rebuild the JS using the `grunt amd` command while in the reportbuilder/amd/ folder Visit the reportbuilder editor for the 'Users' report Click the 'Preview' button, verify the number of rows shown is 5