Fix invalid escape sequences in strings

[SunilMohanAdapa]

• In Python 3.12 and above, these lead to messages such as "SyntaxWarning: invalid escape sequence '\s'". In versions of Python earlier than 3.12, they were DeprecationWarnings. In a later version of Python these will lead to a SyntaxError.

Tests:

• Verify that the new strings are equivalent to the old strings by old_string == new_string in the python interpreter in Python 3.12. old_string throws SyntaxWarning new_string does not.

• Run 'python3 -m py_compile' on each python source file (except legacy files) and ensure that there are no syntax errors or warnings.