Parser::ParseLexedAttribute and Parser::ParseLexedCAttribute should be merged (same for Parser::ParseLexedCAttributeList)

[delcypher]

#90786 introduced Parser::ParseLexedCAttributeList and Parser::ParseLexedCAttribute. These shouldn't need to exist they should be replaced with Parser::ParseLexedAttributeList and Parser::ParseLexedAttribute respectively which appear very similar.

This refactoring would mean that more of the late parsing infrastructure for struct fields in C and for a bunch of things in C++ would be shared.