Diagnostics: Add support for finding hidden tokens (comments)

[KevinEady]

Comments are stored as hidden tokens on the parser's token stream. In order to find the hidden tokens before a given token, access to the token stream is needed. The SourceFile is what keeps the parser, and the compilations SourceFiles are held by the BuilderWorkspace in its source_files member.

The BuilderWorkspace was a heap variable inside CompilerWorkspaceBuilder::build but has now been moved to be a class member of the "root" CompilerWorkspace, so applications can grab the SourceFile for a given compiled file and call sf->get_hidden_tokens_before() like so:

void HoverBuilder::append_comment( const SourceLocation& source_location, std::string& result )
{
  std::string comment;
  const auto& pathname = source_location.source_file_identifier->pathname;
  auto itr = workspace.builder_workspace.source_files.find( pathname );
  auto tokens = workspace.source->get_all_tokens();
  if ( itr != workspace.builder_workspace.source_files.end() )
  {
    auto sf = itr->second;
    auto hidden_tokens = sf->get_hidden_tokens_before( source_location.range.start );

    for ( auto const* token : hidden_tokens )
    {
      auto token_text = Pol::Clib::strtrim( token->getText() );
      if ( token_text.length() == 0 )
      {
        continue;
      }

      comment += "\n" + token_text;
    }
  }
  if ( !comment.empty() )
  {
    result += "\n" + comment;
  }
}

[coveralls]

coverage: 46.275% (+0.003%) from 46.272%
when pulling 6d396ce on ecompile-diagnostics-hidden-tokens
into e34eaee on ecompile-diagnostics.