[ddc] Fix incorrect source maps from JS templates

JS templates should always use their own source information. DDC
was incorrectly caching and reusing templates with the same source
information in various parts of the program. This lead to incorrect
source maps and in some cases compiler crashes when the source map
in a user application pointed to source location in the SDK.

Change-Id: I11607e6f02b894ead1d350e9b3071173ba36a048
Fixes: #43589
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/166122
Reviewed-by: Mark Zhou <[email protected]>
Reviewed-by: Sigmund Cherem <[email protected]>
Commit-Queue: Nicholas Shahan <[email protected]>

Author: nshahan

pkg/dev_compiler/lib/src/kernel/compiler.dart

@@ -5034,7 +5034,7 @@ class ProgramCompiler extends ComputeOnceConstantVisitor<js_ast.Expression>
 
     assert(result is js_ast.Expression ||
         result is js_ast.Statement && node.parent is ExpressionStatement);
-    return result;
+    return result.withSourceInformation(_nodeStart(node));
   }
 
   bool _isNull(Expression expr) =>