change type_tag_parser to pub
change type_tag_parser to pub

There's pub func `parse_type_tags` in type_tag_parser,
It's useful for developer to parse type tags in their third-party tools
Closes: #3852
Approved by: vgao1996

aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,libra/libra,libra/libra,aptos-labs/aptos-core,libra/libra,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core