629 efficient processing dense matrix of strings dsl

[saminbassiri]

[DAPHNE-#629] Enhance String Processing Capabilities in DaphneDSL for DenseMatrices of strings

Summary

This PR closes issue #629, and building on the progress of PR #845. It introduces several enhancements to DaphneDSL, expanding support for string operations on DenseMatrix<std::string>. It covers a range of features to improve the efficiency and flexibility of string handling at the DaphneDSL level.

Changes:

• CSV Reading: Add support for reading CSV files with string values into DenseMatrix<std::string>.
• Unary Operations (Upper/Lower): Implement element-wise (EW) unary operations for converting strings to upper and lower case on c_strings and DenseMatrix<std::string>.
• Reverse and Transpose: Add support for reversing and transposing DenseMatrix<std::string>.
• Recode: Add the ability to recode values in DenseMatrix<std::string>.
• One-Hot Encoding: Enable one-hot encoding functionality for DenseMatrix<std::string>.
• Left/Right Indexing: Add support for left and right indexing on DenseMatrix<std::string>.
• Element-Wise Binary Operations: Implement element-wise binary operations on DenseMatrix<std::string>.
• Casting: Add support for casting DenseMatrix<std::string> to other compatible types.
• Matrix Literal and Reshape: Implement the ability to create DenseMatrix<std::string> using matrix_literal and reshape operations.
• Fill Function: Add support for the fill function to create DenseMatrix<std::string>.

Testing

Initial tests for DenseMatrix<std::string> in DaphneDSL scripts were implemented to verify the functionality of all newly introduced features, ensuring robust support for string operations in dense matrices.