MINOR: tools: add chunk_escape_string() helper function

MINOR: tools: add chunk_escape_string() helper function

This function takes a string appends it to a buffer in a format
compatible with most languages (double-quoted, with special characters
escaped). It handles standard escape sequences like \n, \r, \", \\.

This generic utility is desined to be used for logging or debugging
purposes where arbitrary string data needs to be safely emitted without
breaking the output format. It will be primarily used by the upcoming
dump_all_vars() sample fetch to dump variable contents safely.