Symbol package questions

[mmitche]

There are two questions that we need answered:

• The arcade symbol packages do not appear to have symbols. Why? Is this intentional? Bug?
• https://dev.azure.com/dnceng/internal/_build/results?buildId=2599081 - System.Diagnostics.EventLog's symbol package has most PDBs, but is missing the PDB for the .Messages.dll. This is a project reference in System.Diagnostics.EventLog. Is this correct?

[missymessa]

@hoyosjs can you answer Mitchell's questions, por favor?

[hoyosjs]

The second question led to some changes in the infra to flow PDBs. The first - yeah, while doing some symbols work I realized arcade had turned off symbol indexing due to a third-party dependency blocking indexing. There's infra now to avoid that so we could reenable if we want.