Implement state saving and loading for CPU and Bus, add tests for various functionalities

- Added `state.c` to handle saving and loading the state of the CPU and Bus.
- Implemented CRC32 checksum for data integrity verification during state operations.
- Enhanced `README.md` in tests/roms to document new test commands for decimal, interrupt, Apple I, and nestest.
- Created new test files: `run_apple1.c`, `run_decimal.c`, `run_interrupt.c`, `run_nestest.c`, and `run_vectors.c` to validate the new features.
- Updated `run_tests.c` to include tests for state saving/loading and other functionalities.
- Introduced `test_vectors.py` to facilitate downloading and running JSON test vectors for opcode verification.

include/apple1.h

@@ -0,0 +1,14 @@
+#ifndef APPLE1_H
+#define APPLE1_H
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include "bus.h"
+typedef struct {
+    uint8_t key;bool key_ready;bool stdout_enabled;
+    char output[8192];size_t output_length;
+} Apple1IO;
+void apple1_init(Apple1IO *io,Bus6502 *bus);
+void apple1_key(Apple1IO *io,uint8_t ascii);
+void apple1_enable_stdout(Apple1IO *io,bool enabled);
+#endif