chd.cpp: More API changes

- Have metadata_find return std::error_condition instead of throwing an exception
- Replace the is_XXX predicates with check_is_XXX methods that return a std::error_condition, enabling improved error reporting for cdrom_image_device
- Retain read error information in chd_file_compressor
- Make a bunch of methods noexcept

This mostly restores the changes from cc77207.

Author: ajrhacker

src/devices/imagedev/cdromimg.cpp

@@ -79,9 +79,9 @@ void cdrom_image_device::setup_current_preset_image()
 	m_dvdrom_handle.reset();
 
 	chd_file *chd = current_preset_image_chd();
-	if (chd->is_cd() || (m_gd_compat && chd->is_gd()))
+	if (!chd->check_is_cd() || (m_gd_compat && !chd->check_is_gd()))
 		m_cdrom_handle = std::make_unique<cdrom_file>(chd);
-	else if(m_dvd_compat && chd->is_dvd())
+	else if(m_dvd_compat && !chd->check_is_dvd())
 		m_dvdrom_handle = std::make_unique<dvdrom_file>(chd);
 	else
 		fatalerror("chd for region %s is not compatible with the cdrom image device\n", preset_images_list()[current_preset_image_id()]);
@@ -130,15 +130,31 @@ std::pair<std::error_condition, std::string> cdrom_image_device::call_load()
 	// open the CHD file
 	if (chd)
 	{
-		if (chd->is_cd() || (m_gd_compat && chd->is_gd()))
-			m_cdrom_handle.reset(new cdrom_file(chd));
-		else if (m_dvd_compat && chd->is_dvd())
-			m_dvdrom_handle.reset(new dvdrom_file(chd));
-		else
+		err = chd->check_is_cd();
+		if (err == chd_file::error::METADATA_NOT_FOUND && m_gd_compat)
+			err = chd->check_is_gd();
+		if (!err)
 		{
-			err = image_error::INVALIDIMAGE;
+			m_cdrom_handle.reset(new cdrom_file(chd));
+			return std::make_pair(std::error_condition(), std::string());
+		}
+		if (err != chd_file::error::METADATA_NOT_FOUND)
 			goto error;
+
+		if (m_dvd_compat)
+		{
+			err = chd->check_is_dvd();
+			if (!err)
+			{
+				m_dvdrom_handle.reset(new dvdrom_file(chd));
+				return std::make_pair(std::error_condition(), std::string());
+			}
+			if (err != chd_file::error::METADATA_NOT_FOUND)
+				goto error;
 		}
+
+		err = image_error::INVALIDIMAGE;
+		goto error;
 	}
 	else
 	{