refactor(packages/codegen): add `writeWithMapNamedJSXNoLast` (#25980)

Writing mappings for JSX identifiers requires different logic than for normal `Identifiers`.

- Add specialized function `writeWithMapNamedJSXNoLast` for writing `JSXIdentifier`s.
- Move the logic for getting original name of a `JSXIdentifier` into a separate function.
- Branch on an `isJSXIdentifier` param passed in to `markMapNamed`, to decide which function to use to get original identifier name.

The main motivation is to avoid having to pass `node` into `originalNameFromSource`, where reading `node.type` is a polymorphic access (because `node` could be an `Identifier`, an `PrivateIdentifier` or `JSXIdentifier`). This is part of a broader move to remove the reliance of all `write` and `markMap` functions on receiving polymorphic/megamorphic `node` params (later PRs in this stack).