Feature: Add f_string_dynamic_strip_null() and f_string_dynamic_strip_null_range().

Feature: Add f_string_dynamic_strip_null() and f_string_dynamic_strip_null_range().

The ability to strip out NULLs from a given string as a common function is needed.

Provide two similar but different functions.
The f_string_dynamic_strip_null() moves the NULLs to the end of the string and the shrinks the string used length as appropriate.
The f_string_dynamic_strip_null_range() shifts all of the NULLs found to the end of the given range without modifying the array used length.

Unit tests are added.

Only basic logic is applied and so there is no especially focused optimization in the parsing logic.