Print hash expansions in the hash_testing error messages.

I find that this makes it much easier to understand the problems.

Example error without this change:
Hash expansion of #0(24-byte object <00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00>) is a suffix of the hash expansion of #1(24-byte object <00-CB E3-BF FB-12 00-00 F0-FF BE-9D FD-7F 00-00 B8-0D 04-1C 59-7F 00-00>).

Example error with this change:
Hash expansion of #0(24-byte object <00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00>);[

0x0000:  0000 0000 0000 0000
] is a suffix of the hash expansion of #1(24-byte object <00-EC E3-FF F8-31 00-00 50-10 90-94 FF-7F 00-00 40-98 E8-33 5E-7F 00-00>);[

0x0000:  2ebc 2196 d3ab 37da

0x0000:  0000 0000

0x0000:  0000 0000 0000 0000
].
PiperOrigin-RevId: 708356078
Change-Id: Iab9060d70eeb051c5a28786e4542f49629165ce0

absl/hash/hash_testing.h

@@ -244,7 +244,8 @@ VerifyTypeImplementsAbslHashCorrectly(const Container& values, Eq equals) {
       if (v.expand() != expected) {
         return testing::AssertionFailure()
                << "Values " << c[0].ToString() << " and " << v.ToString()
-               << " evaluate as equal but have an unequal hash expansion.";
+               << " evaluate as equal but have unequal hash expansions ("
+               << expected << " vs. " << v.expand() << ").";
       }
     }
 
@@ -256,17 +257,18 @@ VerifyTypeImplementsAbslHashCorrectly(const Container& values, Eq equals) {
         case SpyHashState::CompareResult::kEqual:
           return testing::AssertionFailure()
                  << "Values " << c[0].ToString() << " and " << c2[0].ToString()
-                 << " evaluate as unequal but have an equal hash expansion.";
+                 << " evaluate as unequal but have an equal hash expansion:"
+                 << c2_hash << ".";
         case SpyHashState::CompareResult::kBSuffixA:
           return testing::AssertionFailure()
-                 << "Hash expansion of " << c2[0].ToString()
+                 << "Hash expansion of " << c2[0].ToString() << ";" << c2_hash
                  << " is a suffix of the hash expansion of " << c[0].ToString()
-                 << ".";
+                 << ";" << expected << ".";
         case SpyHashState::CompareResult::kASuffixB:
           return testing::AssertionFailure()
-                 << "Hash expansion of " << c[0].ToString()
-                 << " is a suffix of the hash expansion of " << c2[0].ToString()
-                 << ".";
+                 << "Hash expansion of " << c[0].ToString() << ";"
+                 << expected << " is a suffix of the hash expansion of "
+                 << c2[0].ToString() << ";" << c2_hash << ".";
         case SpyHashState::CompareResult::kUnequal:
           break;
       }