fix: Add Extra Check for Reformatted Root Node in GetNode (backport #1007)

[mergify]

Problem Description

When the root node is reformatted due to pruning, its nodeKey changes from (version, 1) to (version, 0). As a result:

1.	This version becomes invisible during a root search.
2.	If a node in the next version references the reformatted node, it becomes inaccessible.

Proposed Solution

Add an extra check in the GetNode function to handle reformatted root nodes. This ensures that:

•	Reformatted nodes with nodeKey (version, 0) remain accessible.
•	References to these nodes from subsequent versions are correctly resolved.

Summary by CodeRabbit

• New Features

  • Introduced a new test to validate the behavior of the MutableTree after version deletions.
  • Added new APIs: DeleteVersionsFrom(int64) and GetLatestVersion.

• Bug Fixes

  • Enhanced the GetNode method to improve retrieval logic for nodes, ensuring better handling of cases with nil buffers and legacy nodes.

• Documentation

  • Updated the changelog to reflect recent improvements and fixes, including a new section for bug fixes and detailed descriptions of changes.

---

This is an automatic backport of pull request #1007 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of cf74234 has failed:

On branch mergify/bp/release/v1.2.x/pr-1007
Your branch is up to date with 'origin/release/v1.2.x'.

You are currently cherry-picking commit cf74234.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   CHANGELOG.md
	modified:   nodedb.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   mutable_tree_test.go

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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