Add typed sum aggregation methods to NumberExpression

[jparams]

Motivation

• Ensure aggregate sum results map to appropriate numeric types (double, long, BigDecimal, BigInteger) rather than always using the expression's original type.
• Provide convenience methods to explicitly request the desired aggregation return type for NumberExpression.

Description

• Added imports for BigDecimal and BigInteger and a private generic helper method sum(Class<P>) to create typed sum aggregation expressions.
• Refactored sum() to delegate to the generic sum helper and added typed convenience methods sumDouble(), sumLong(), sumBigDecimal(), and sumBigInteger().
• Added @SuppressWarnings("unchecked") where appropriate to handle generic casting in the new helper and sum() implementation.
• Extended NumberExpressionTest with tests sumBigDecimal_has_bigDecimal_type, sumBigInteger_has_bigInteger_type, sumDouble_has_double_type, and sumLong_has_long_type to verify the resulting aggregation types.

Testing

• Ran the unit tests in NumberExpressionTest which include the newly added type-assertion tests; all tests passed.
• Executed the module unit test suite locally (mvn -Dtest=NumberExpressionTest test) and observed successful completion.

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Codex Task