Gather all string operators in one standard file

[elronbandel]

This PR addresses the scattered nature of string/text operators across different modules—operators and processors—making them challenging to locate, reuse, and maintain a consistent standard while tracking changes. The goal is to consolidate all string/text operators into a single file, enhancing discoverability and standardization. This includes thorough documentation, an introductory guide listing all operators, and a reduction in their number to streamline usage. Additionally, this PR introduces tests for each operator to ensure reliability. Importantly, these changes are designed to be 100% backward compatible.