Implement RHT.GC

[hackerwins]

What this PR does / why we need it:

Implement RHT.GC

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Additional documentation:

Checklist:

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

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 45.38462% with 71 lines in your changes are missing coverage. Please review.

Project coverage is 50.64%. Comparing base (18224f1) to head (ccacc0a).

:exclamation: Current head ccacc0a differs from pull request most recent head 1e5ca67

Please upload reports for the commit 1e5ca67 to get more accurate results.

Files	Patch %	Lines
pkg/document/crdt/tree.go	36.06%	37 Missing and 2 partials :warning:
pkg/document/crdt/rht.go	66.66%	16 Missing and 1 partial :warning:
pkg/document/crdt/root.go	18.75%	12 Missing and 1 partial :warning:
pkg/document/change/context.go	0.00%	2 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #864      +/-   ##
==========================================
- Coverage   50.81%   50.64%   -0.17%     
==========================================
  Files          70       70              
  Lines       10285    10342      +57     
==========================================
+ Hits         5226     5238      +12     
- Misses       4530     4573      +43     
- Partials      529      531       +2     

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