refactor(compiler): replace Comment nodes with leadingComments property (#38811)

Common AST formats such as TS and Babel do not use a separate
node for comments, but instead attach comments to other AST nodes.
Previously this was worked around in TS by creating a `NotEmittedStatement`
AST node to attach the comment to. But Babel does not have this facility,
so it will not be a viable approach for the linker.

This commit refactors the output AST, to remove the `CommentStmt` and
`JSDocCommentStmt` nodes. Instead statements have a collection of
`leadingComments` that are rendered/attached to the final AST nodes
when being translated or printed.

PR Close #38811

packages/compiler-cli/src/transformers/util.ts

@@ -94,3 +94,12 @@ export function ngToTsDiagnostic(ng: Diagnostic): ts.Diagnostic {
     length,
   };
 }
+
+/**
+ * Strip multiline comment start and end markers from the `commentText` string.
+ *
+ * This will also strip the JSDOC comment start marker (`/**`).
+ */
+export function stripComment(commentText: string): string {
+  return commentText.replace(/^\/\*\*?/, '').replace(/\*\/$/, '').trim();
+}