Added factory for read data

[a-chumagin]

• Updates the prepare-unit-tests target in the Makefile to install the moto package in addition to the pytest package.
• Adds a new Python module data_source_factory.py in the functions/data_test directory.
• Defines an abstract class DataSource and several concrete subclasses in data_source_factory.py, each representing a type of data source.
• Defines a DataSourceFactory class in data_source_factory.py that creates instances of these subclasses based on the input parameters passed to it.
• Defines a read method for each data source subclass in data_source_factory.py, which reads data from the corresponding source and returns it as a Pandas DataFrame.
• Defines a variable ENV in data_source_factory.py that stores the environment name read from the ENVIRONMENT environment variable.
• unit tests