[V2] [Fix] Skip debug ID injection for modulesOnly bundles

[sbarrio]

What does this PR do?

Reported by: #1297

The metro serializer crashed when Metro asked for a modulesOnly bundle (lazy imports / split chunks), because those bundles don't carry a pre modules section that the Debug ID injection step relies on.

This fix skips running the serializer for modulesOnly=true bundles, avoiding the crash.

Motivation

The debug id implementation should not clash with the dev metro server.

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