Part of #43927. Dependent on #45166. Introduce two methods PacketsDefinition.define_type(alias: str, meaning: str) -> None and PacketsDefinition.resolve_type(type_text: str) -> str and pass the latter to the Packet and Field parsing code instead of the bare types dict. The plan is that in some future patch, the return type of resolve_type() will be replaced with one representing an already-parsed type, so Field.parse() no longer needs to care about type parsing.
alienvalkyrie 
Part of #43927. Dependent on #45166. Introduce two methods PacketsDefinition.define_type(alias: str, meaning: str) -> None and PacketsDefinition.resolve_type(type_text: str) -> str and pass the latter to the Packet and Field parsing code instead of the bare types dict. The plan is that in some future patch, the return type of resolve_type() will be replaced with one representing an already-parsed type, so Field.parse() no longer needs to care about type parsing.