Refactor: separate estimators into separate files

[TomeHirata]

Refactor the init.py and separate the contents into multiple files

[Copilot]

Pull Request Overview

This PR refactors the __init__.py file by extracting classes into separate modules to improve code organization and maintainability.

• Moves base class and concrete estimator implementations to dedicated modules
• Creates separate files for stratified, simple, and local distribution estimators
• Simplifies the main __init__.py to focus on imports and exports

Reviewed Changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
dte_adj/__init__.py	Refactored to import classes from separate modules instead of defining them inline
dte_adj/base.py	Contains the base DistributionEstimatorBase abstract class with common functionality
dte_adj/stratified.py	Contains stratified distribution estimator implementations
dte_adj/simple.py	Contains simple distribution estimator implementations that inherit from stratified classes
dte_adj/local.py	Contains local distribution estimator implementations for LDTE and LPTE

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