fix: contract not compiling in presence of meta-ligo terms

type:fixed

• no more Test stubs in std_lib
• always include meta-ligo types in initial environment
• add a pass in self_ast_aggregated to remove all meta-ligo expression (if option.middle_end.test == true) . see pruge_meta_ligo

Changelog details:

• fix a regression where contract could not compile in presence of meta-ligo expressions (automatically remove such expressions)