Fix Coverity issue #545159 and all related issues.

Don't use fmt::format() when formatting wxString objects.  It will throw
an exception on an argument type mismatch which isn't handled in most
code paths.

This also prevents the conversion of the fmt::format() arguments from
wxString to std::string and the result from std::string back to wxString
for the return value.

https://scan8.scan.coverity.com/#/project-view/22886/10844?selectedIssue=545159

common/lib_id.cpp

@@ -275,7 +275,7 @@ bool LIB_ID::isLegalLibraryNameChar( unsigned aUniChar )
 const wxString LIB_ID::GetFullLibraryName() const
 {
     if( m_subLibraryName.empty() )
-        return m_libraryName.c_str();
+        return m_libraryName;
 
-    return fmt::format( "{} - {}", m_libraryName.c_str(), m_subLibraryName.c_str() );
+    return wxString::Format( wxS( "%s - %s" ), m_libraryName.c_str(), m_subLibraryName.c_str() );
 }