重构代码的架构设计，增加测试单元，提高代码可靠性

tests/test_p0_utf8_next.c

@@ -0,0 +1,27 @@
+#include "../src/Drv/lcd/lcd_text.h"
+#include "test_common.h"
+
+int main(void)
+{
+    uint32_t unicode = 0;
+    const unsigned char ascii[] = "A";
+    const unsigned char u2[] = {0xC2, 0xA2, 0x00};       /* U+00A2 */
+    const unsigned char u3[] = {0xE4, 0xBD, 0xA0, 0x00}; /* U+4F60 */
+    const unsigned char invalid[] = {0xF0, 0x00};        /* 4-byte start not supported */
+    const unsigned char truncated2[] = {0xC2, 0x00};
+    const unsigned char truncated3[] = {0xE4, 0xBD, 0x00};
+
+    ASSERT_EQ_INT(1, utf8_next(ascii, &unicode));
+    ASSERT_EQ_U32(0x41u, unicode);
+
+    ASSERT_EQ_INT(2, utf8_next(u2, &unicode));
+    ASSERT_EQ_U32(0x00A2u, unicode);
+
+    ASSERT_EQ_INT(3, utf8_next(u3, &unicode));
+    ASSERT_EQ_U32(0x4F60u, unicode);
+
+    ASSERT_EQ_INT(0, utf8_next(invalid, &unicode));
+    ASSERT_EQ_INT(0, utf8_next(truncated2, &unicode));
+    ASSERT_EQ_INT(0, utf8_next(truncated3, &unicode));
+    return 0;
+}