fix: remove IFileAccessor and add FileAccessor

[kochounoyume]

No description provided.

[Copilot]

Pull Request Overview

This PR removes the IFileAccessor interface and replaces it with an abstract FileAccessor class that standardizes file system operations for local preferences. Key changes include:

• Removal of IFileAccessor and its associated default implementation.
• Introduction of FileAccessor as an abstract base class with a nested DefaultFileAccessor.
• Updates in LSAccessor, MessagePackLocalPrefs, and JsonLocalPrefs to use FileAccessor instead of IFileAccessor.

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/LocalPrefs/IFileAccessor.cs	Removed the obsolete interface in favor of an abstract class.
src/LocalPrefs/FileAccessor.cs	Introduced a new abstract class with a nested default implementation.
src/LocalPrefs.Unity/Packages/jp.andantetribe.localprefs/Runtime/LocalPrefs.cs	Updated file accessor instantiation to reference the new implementations.
src/LocalPrefs.Unity/Packages/jp.andantetribe.localprefs/Runtime/LSAccessor.cs	Changed the base class from IFileAccessor to FileAccessor.
src/LocalPrefs.MessagePack/MessagePackLocalPrefs.cs	Updated constructor parameters and property types from IFileAccessor to FileAccessor.
src/LocalPrefs.Json/JsonLocalPrefs.cs	Updated constructor parameters and property types from IFileAccessor to FileAccessor.

Comments suppressed due to low confidence (2)

src/LocalPrefs/FileAccessor.cs:7

• [nitpick] Consider expanding the XML documentation for FileAccessor to clearly explain its role as a replacement for IFileAccessor and to aid users during migration.

public abstract class FileAccessor(string savePath)

src/LocalPrefs.MessagePack/MessagePackLocalPrefs.cs:32

• Ensure that the change from IFileAccessor to FileAccessor, which may be a breaking change for consumers, is clearly documented in the migration guide and any related dependency injection registrations.

: this(FileAccessor.Create(savePath), resolver == null ? null : MessagePackSerializer.DefaultOptions.WithResolver(resolver))