Handle concurrent editing and styling in Tree

[hackerwins]

What this PR does / why we need it:

Handle concurrent editing and styling in Tree

We will use maxCreatedAtMapByActor until the introduction of VersionVector.

• Related to Introduce VersionVector to detect the relationship between changes #800

Which issue(s) this PR fixes:

Address #788

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Additional documentation:

Checklist:

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

[codecov]

Codecov Report

Attention: Patch coverage is 57.14286% with 39 lines in your changes are missing coverage. Please review.

Project coverage is 50.81%. Comparing base (a82995b) to head (1dea4eb).

Files	Patch %	Lines
pkg/document/crdt/tree.go	63.26%	17 Missing and 1 partial ⚠️
api/converter/to_pb.go	20.00%	8 Missing ⚠️
api/converter/from_pb.go	0.00%	7 Missing ⚠️
pkg/document/crdt/rga_tree_split.go	80.00%	3 Missing ⚠️
pkg/document/crdt/text.go	70.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #854      +/-   ##
==========================================
- Coverage   50.81%   50.81%   -0.01%     
==========================================
  Files          70       70              
  Lines       10255    10285      +30     
==========================================
+ Hits         5211     5226      +15     
- Misses       4516     4530      +14     
- Partials      528      529       +1     

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