[GR-77549] Fix a race condition in AnalysisObject.getInstanceFieldTypeStore(...)

[graalvmbot]

Fixes a race condition:

• Thread A creates a new FieldTypeStore.
• Thread A publishes it into instanceFieldsTypeStore via compareAndSet(...).
• Before Thread A calls fieldStore.init(...), Thread B obtains that same store and uses its read/write flow.
• Before Thread A calls linkFieldFlows(...), Thread B sees a store whose:
  • initial field flow is not connected to the store’s write flow;
  • read flow is not connected to the field’s global sink flow;
  • split-store write-to-read link may also be absent.
• Thread B can therefore process a load/store using an empty or incomplete type state.