Always convert printed objects to strings in JS (#2741)

This makes browsers match the behavior in Dart and Node, and
specifically fixes a bug where warnings were emitted as `StringBuffer`
objects rather than console messages.

Author: nex3

CHANGELOG.md

@@ -5,6 +5,9 @@
 * Fix a crash when manually constructing a `SassCalculation` for `'calc'` with
   an argument that can't be simplified.
 
+* Properly emit deprecation warnings as text rather than `StringBuffer` objects
+  when running in a browser.
+
 ## 1.97.3
 
 * Fix a bug where nesting an at-rule within multiple style rules in plain CSS

lib/src/io/js.dart

@@ -39,15 +39,15 @@ void safePrint(Object? message) {
   if (_process case var process?) {
     process.stdout.write("${message ?? ''}\n");
   } else {
-    console.log(message ?? '');
+    console.log(message?.toString() ?? '');
   }
 }
 
 void printError(Object? message) {
   if (_process case var process?) {
     process.stderr.write("${message ?? ''}\n");
   } else {
-    console.error(message ?? '');
+    console.error(message?.toString() ?? '');
   }
 }