Resolve nested classes, generic field counts, and inherited statics

[ero-qt]

Depends on #145.
Part of #141.

Three lookups the walk couldn't answer yet:

• Nested classes: get_class("Ns.Outer+Inner"), written the way .NET writes it. The leaf name matches, the enclosing chain checks the rest. Builds without the enclosing offset measured miss cleanly.
• Generic field counts: a generic instance declares no count of its own, so mono reads it from the definition through the instantiation descriptor. IL2CPP already puts the count on the instance.
• Inherited statics: a static field found on a parent measures into the parent's own static table. wait_get_static_instance and UnityPointer roots were reading the starting class's table instead.

The offsets tables grow the members these need, measured per build. Tests cover each lookup and the miss paths, plus a poll-once helper so the wait_ methods can be pinned without hanging.