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_hz12_get.c

@@ -0,0 +1,14 @@
+#include "../src/Drv/lcd/ascii.h"
+#include "test_common.h"
+
+int main(void)
+{
+    const uint8_t* hit = utf8_hz12_get(0x4F60u); /* 你 */
+    const uint8_t* miss_low = utf8_hz12_get(0x0001u);
+    const uint8_t* miss_high = utf8_hz12_get(0x10FFFFu);
+
+    ASSERT_TRUE(hit != NULL);
+    ASSERT_TRUE(miss_low == NULL);
+    ASSERT_TRUE(miss_high == NULL);
+    return 0;
+}