bug fix: to_string(char) is not the right way to create string from char

indeed, `to_string(char)` converts the ascii value to a string (e.g. 'L' -> 76).
use `string(&char, size)` instead.

include/dlaf/blas/enum_parse.h

@@ -12,13 +12,15 @@
 
 /// @file
 
+#include <string>
+
 #include <blas/util.hh>
 
 namespace dlaf::internal {
 
 inline blas::Uplo char2uplo(const char uplo_c) {
   blas::Uplo uplo;
-  blas::from_string(std::to_string(uplo_c), &uplo);
+  blas::from_string(std::string(&uplo_c, 1), &uplo);
   return uplo;
 }