The debugger should be notified whenever a new Module is created so it
displayed properly. Without this change, the Module is only displayed once,
regardless of the number of times it is referenced (by other Workers, say).
That is potentially reasonable behavior, but it doesn't match the way
JavaScript does it.

With this change, the debugger will display the sources like this:

```
▼ top
  ▶ localhost
  ▼ wasm
    ▼ wasm-82570336
        wasm-82570336-0

▼ worker.js
  ▶ localhost
  ▼ wasm
    ▶ wasm-82570336
```

Change-Id: I61177e8a07e36ea8e2234aa25e75b1489c9da95f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1666616Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Ben Smith <binji@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62297}