[Feature Request]: Implement a teal_transform_module

[gogonzo]

Feature description

See this file where most of the work is done.

• teal_transform_module's ui and server should be consumed in ui/srv_nested_tabs just after creation of teal_data object.
• Beware that instead of data (teal_data), datasets (FilteredData) object could be still used in a module, and transform can't be performed on FilteredData. Please include transform under condition is_arg_used(modules$server, "data")
• Add validates for reactive teal_data find here