`VirtualNodeCache`: wrong check in `deleteInternal()`?

[swirlds-automation]

Calling throwIfLeafImmutable() in deleteInternal() is inconsistent with the logic of the class and looks like a copy-paste error. Changing it to throwIfInternalsImmutable(), which is also used in putInternal(), causes 9 unit tests to fail, however.

[swirlds-automation]

I think this is intentional and I have to remember why. Even though the name looks wrong. It has to do with what phase we delete internals in. I believe internals are only deleted during handle transaction, which is when leafs are mutable. Internals are created during hashing when leafs are immutable. _{author:rbair23, createdAt:2022-02-17T18:27:15Z, updatedAt=2022-02-17T18:27:15Z}

[swirlds-automation]

deleteInternal() is called only from VirtualRootNode.remove(K key) so yes, it can happen only when leaves are mutable (and internals are immutable). That is confusing. Maybe the logic should be internalized in VirtualNodeCache without making deleteInternal() public with very specific conditions of when and how it could be invoked (making it an ad hoc method). _{author:OlegMazurov, createdAt:2022-02-17T18:49:02Z, updatedAt=2022-02-17T18:49:02Z}

[swirlds-automation]

deleteInternal() is used in the same context and serves a similar purpose as clearLeafPath(long path). It should be renamed clearInternalPath and placed along with clearLeafPath. throwIfLeafImmutable() will not create confusion in that setting (helped by a clarifying comment). _{author:OlegMazurov, createdAt:2022-02-18T03:55:53Z, updatedAt=2022-02-18T03:55:53Z}

[swirlds-automation]

_{migrated from: url=https://github.com/swirlds/swirlds-platform/issues/4825 author:OlegMazurov, #:4825, createdAt:2022-02-17T16:31:24Z, updatedAt=2023-02-22T03:15:05Z labels=Code Cleanup,Platform Virtual Map,Platform Data Structures,Migration:Data}