Apply GCPair to TreeNode, TextNode

[hackerwins]

What this PR does / why we need it:

Apply GCPair to TreeNode, TextNode

This commit is a follow-up task of #864, applying GCPair for TextNode and TreeNode. Additionally, when generating a document from the root, this commit registers GCPair in the cache.

Which issue(s) this PR fixes:

Address #763

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Additional documentation:

Checklist:

• [x] Added relevant tests or not required
• [x] Didn't break anything

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 49.74359% with 98 lines in your changes are missing coverage. Please review.

Project coverage is 50.59%. Comparing base (bd46419) to head (d2ab002).

Files	Patch %	Lines
pkg/document/crdt/tree.go	49.52%	53 Missing :warning:
pkg/document/crdt/text.go	3.70%	26 Missing :warning:
pkg/document/crdt/root.go	57.57%	13 Missing and 1 partial :warning:
pkg/document/crdt/rht.go	0.00%	3 Missing :warning:
pkg/document/crdt/rga_tree_split.go	91.30%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #866 +/- ## ========================================== - Coverage 50.59% 50.59% -0.01% ========================================== Files 70 70 Lines 10350 10389 +39 ========================================== + Hits 5237 5256 +19 - Misses 4581 4602 +21 + Partials 532 531 -1 ```

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