GC events from Native AOT don't contain type names

[agocke]

The problem is that GC events from EventSource in Native AOT contain type IDs, not type names. The correlation between the type IDs (MethodTable pointers?) and the type names isn't possible to determine for a user.

We should have some way to produce a trace with names rather than IDs.

Some options:

1. Tooling somehow connects the two and displays the trace with names (maybe using the PDBs).
2. Native AOT somehow extracts the names during event creation and produces events with names instead of IDs.
3. Native AOT extracts the names during some post-event creation, but still produces a trace with names instead of IDs.

[filipnavara]

Related: #108083, dotnet/diagnostics#4856

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[agocke]

@noahfalk @MichalStrehovsky @tommcdon would appreciate your opinion on the right implementation here. I don’t have any preference right now.

[MichalStrehovsky]

Type name can be computed from a MethodTable pointer using managed code whenever it's necessary. We do not have a fully computed type name for each MethodTable available at all times (we likely don't want to keep the type names for everything around in memory indefinitely because the motivation for native AOT is low memory use). We can piece the type name together when necessary from metadata.

So the restriction from the runtime side is:

• We need to be able to run managed code.
• It must be okay for the managed code to take a while to run (parsing metadata, walking constructed type hierarchy, piecing the name together from individual dotted/namespace/nested type components).

[MichalStrehovsky]

We've decided that debug symbols will be used to decode this at runtime. Work was done so that we generate everything necessary for tools to do this. Perfview can now show type names properly. Similar work can be done in other tools such as in gcdump. This is tracked in dotnet/diagnostics#4856. Closing.