test: add BigInt test for isDeepStrictEqual

Add some BigInt tests for test-util-isDeepStrictEqual to get 100%
coverage for lib/internal/util/comparisons.js.

PR-URL: #25932
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-util-isDeepStrictEqual.js

@@ -447,6 +447,8 @@ assert.strictEqual(
   notUtilIsDeepStrict(boxedString, Object('test'));
   boxedSymbol.slow = true;
   notUtilIsDeepStrict(boxedSymbol, {});
+  utilIsDeepStrict(Object(BigInt(1)), Object(BigInt(1)));
+  notUtilIsDeepStrict(Object(BigInt(1)), Object(BigInt(2)));
 }
 
 // Minus zero