Revert "[NEW] Engagement Statistics (#24777)" (#24989)

app/api/server/v1/users.js

app/importer-csv/server/importer.js

app/importer-hipchat-enterprise/server/importer.js

app/importer-slack-users/server/importer.js

app/importer-slack/server/importer.js

app/importer/server/classes/ImportDataConverter.ts

app/lib/server/methods/sendInvitationEmail.js

app/lib/server/startup/email.ts

app/models/server/models/Messages.js

app/models/server/models/Rooms.js

app/models/server/models/Users.js

app/statistics/server/lib/getServicesStatistics.ts

app/statistics/server/lib/statistics.ts

definition/IImportUser.ts

definition/IStats.ts

definition/IUser.ts

server/services/team/service.ts