tests: add prof_send_raw

Allow sending byte sequences to the Profanity PTY without a newline.
Now we can simulate control characters, specifically the `TAB` key
(`\t`), to trigger autocompletion.

tests/functionaltests/proftest.h

@@ -28,6 +28,7 @@ void prof_start(void);
 void prof_connect(void);
 void prof_connect_with_roster(const char* roster);
 void prof_input(const char* input);
+void prof_send_raw(const char* bytes);
 
 int prof_output_exact(const char* text);
 int prof_output_regex(const char* text);