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
d795a00137