Add JSON marshal/unmarshal support

[ghosind]

For #18, this PR adds MarshalJSON and UnmarshalJSON methods for the collections and dictionaries.

There are two ways to marshal/unmarshal the types to JSON:

• Invoke the MarshalJSON / UnmarshalJSON:

s := set.NewHashSet[int]()
b, err := s.MarshalJSON()

• Use json.Marshal/json.Unmarshal:

s := set.NewHashSet[int]()
b, err := json.Marshal(s)

[codecov]

Codecov Report

❌ Patch coverage is 75.55556% with 22 lines in your changes missing coverage. Please review.
✅ Project coverage is 93.04%. Comparing base (9743c82) to head (767c48b).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
dict/sync_dict.go	75.00%	3 Missing and 3 partials ⚠️
list/linked_list.go	57.14%	4 Missing and 2 partials ⚠️
dict/hash_dict.go	75.00%	1 Missing and 1 partial ⚠️
list/array_list.go	75.00%	1 Missing and 1 partial ⚠️
list/copy_on_write_array_list.go	81.81%	1 Missing and 1 partial ⚠️
set/hash_set.go	80.00%	1 Missing and 1 partial ⚠️
set/sync_set.go	86.66%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #22      +/-   ##
==========================================
- Coverage   94.20%   93.04%   -1.16%     
==========================================
  Files          21       21              
  Lines        1725     1539     -186     
==========================================
- Hits         1625     1432     -193     
+ Misses         73       70       -3     
- Partials       27       37      +10     

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[Copilot]

Pull Request Overview

This PR adds JSON marshaling and unmarshaling support to all collection and dictionary types by implementing MarshalJSON and UnmarshalJSON methods. The changes enable both direct method calls and usage with the standard json.Marshal/json.Unmarshal functions.

Key changes:

• Added JSONMarshaler and JSONUnmarshaler interface definitions to the core Collection and Dict interfaces
• Implemented JSON serialization for all set, list, and dictionary types (sets/lists as arrays, dicts as objects)
• Added comprehensive test coverage for JSON operations across all implementations
• Refactored test helper type names for consistency (e.g., setTestConstructor → setConstructor)

Reviewed Changes

Copilot reviewed 17 out of 17 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
encoding.go	Defines JSONMarshaler and JSONUnmarshaler interface aliases
collection.go	Adds JSON interface requirements to Collection interface
dict.go	Adds JSON interface requirements to Dict interface
set/hash_set.go	Implements MarshalJSON/UnmarshalJSON for HashSet
set/sync_set.go	Implements MarshalJSON/UnmarshalJSON for thread-safe SyncSet
list/array_list.go	Implements MarshalJSON/UnmarshalJSON for ArrayList
list/linked_list.go	Implements MarshalJSON/UnmarshalJSON for LinkedList with zero-value handling
list/copy_on_write_array_list.go	Implements MarshalJSON/UnmarshalJSON for CopyOnWriteArrayList
dict/hash_dict.go	Implements MarshalJSON/UnmarshalJSON for HashDict
dict/sync_dict.go	Implements MarshalJSON/UnmarshalJSON for thread-safe SyncDict
set/set_test.go	Adds testSetJSON and consolidates test helpers; renames constructor type
set/hash_set_test.go	Removes redundant test calls (moved to common testSet)
set/sync_set_test.go	Removes redundant test calls (moved to common testSet)
set/set_go123_test.go	Updates function signature to use renamed constructor type
list/list_test.go	Adds testListJSON for JSON operations testing
dict/dict_test.go	Adds testDictJSON and renames constructor type for consistency
dict/dict_go123_test.go	Updates function signatures to use renamed constructor type

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[Copilot]

Pull Request Overview

Copilot reviewed 17 out of 17 changed files in this pull request and generated no new comments.

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