tests: add hello2, simple, banktest smoke tests

hello2 — stdio vs conio output API comparison (fast/no-attr vs
slower/attributed), also exercises textcolor/textbackground.
simple — packed 2-bit style array bit-twiddling smoke test.
banktest — __banked function calls across two explicit banks in huge
memory mode.

hello2.c updated to call the renamed gettextmode/settextmode (see the
conio rename in 5e5e70d).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/banktest/bank2.c

@@ -0,0 +1,11 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <sprinter.h>
+
+uint16_t bank2var = 0;
+
+void bank2_func(void) __banked
+{
+    printf("BANK2: hello from the second bank, phys page = 0x%02X, var = %u\n", _io_page_w3, bank2var);
+}
+