Combine source-build pre-build report entries for one package

Currently pre-build reports contain an entry for every package in every project, resulting in multiple mentions of the same pre-build if it is used in multiple projects:

```xml

```

I believe it would benefit general readability if one package ID / version combination had a single entry with file paths listed as the entries metadata. Something like this:

```xml

```

Some of the things we should be wary of:
- PowerBI report exists that consumes these reports; any changes to the structure should be also reflected there