[front end] Add args to Template class.

This is part of a series of CLs that will standardize CFE error
reporting to always use `codeFoo.withArguments(...)` when reporting
errors that take arguments and `codeFoo` when reporting errors that
don't take arguments, rather than `templateFoo.withArguments(...)`
when reporting errors that take arguments and `messageFoo` when
reporting errors that don't take arguments. This change will have two
advantages:

- It will lend greater consistency to the CFE codebase, by allowing
  the same `code...` objects to be used both to name error codes
  (e.g., in test expectations) and to report errors. This will allow
  everything associated with a certain error code to be found using a
  single invocation of "Find References" in the editor, rather than
  having to search separately for uses of the code and the message or
  template.

- It should hopefully make the experience of writing code that reports
  errors more pleasant, since it will no longer be necessary to look
  up an error to see whether it takes arguments before using it;
  instead, the developer will be able to type the name of the message
  `code...` declaration, and then use autocompletion to see whether
  `.withArguments(...)` is required.

In this CL, the arguments `index`, `analyzerCodes`, and `severity` are
added to the `Template` constructor, and those arguments are supplied
by the generated code. But the arguments are not used yet. In follow
up CLs, I will change the `Template` class so that it extends `Code`
and passes these arguments along to the `Code` constructor. This in
turn will allow the `Template` objects to serve the dual role of being
either a template or an error code, in much the same way that for
errors that don't take arguments, the `MessageCode` objects serve the
dual role of being either an error code or an error message.

Change-Id: Id8d7afab0845048db96d57f68ca91259a6dbaf5e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/443001
Reviewed-by: Johnni Winther <[email protected]>
Commit-Queue: Paul Berry <[email protected]>

Author: stereotype441

pkg/_fe_analyzer_shared/lib/src/messages/codes.dart

@@ -118,6 +118,9 @@ class Template<T> {
     this.correctionMessageTemplate,
     required this.problemMessageTemplate,
     required this.withArguments,
+    int index = -1,
+    List<String>? analyzerCodes,
+    CfeSeverity severity = CfeSeverity.error,
   });
 
   @override