[OneExplorer] Review the necessity of NodeMap

[dayo09]

What?

NodeMap store path to node relationship.
To fulfill this functionality, node insertion/deletion should be related to all the file creation/deletion.

Initially it was introduced to keep node status in spite of hide/show status.
Let's check if it's really needed. Maybe nodes can be conditionally mapped to TreeItem, so that node map can be deprecated.

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DRAFT: #1717

[dayo09]

Usages

It maps filesystem change to node

• onDidDelete, onDidCreate, onDidChange
  • events take file uri. NodeMap helps getting the corresponding node instantly.
• revealInOneExplorer
  • it also takes file uri. ditto.