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/bank1.c

@@ -0,0 +1,18 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <sprinter.h>
+
+uint16_t bank1var = 0;
+extern uint16_t bank2var;
+
+void bank1_func(void) __banked
+{
+    printf("BANK1: hello from the first bank, phys page = 0x%02X, var = %u\n", _io_page_w3, bank1var);
+}
+
+void bank1_func2(uint16_t x) __banked
+{
+    printf("BANK1: hello from the first bank, phys page = 0x%02X, set var in SECOND bank to %u\n", _io_page_w3, x);
+    bank2var = x;
+}
+