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/bus.h

@@ -5,13 +5,20 @@
 #include <stdint.h>
 #include "memory.h"
 
-typedef struct Bus6502 {
+typedef struct Bus6502 Bus6502;
+typedef bool (*bus_read_hook_t)(void *userdata,uint16_t addr,uint8_t *value);
+typedef bool (*bus_write_hook_t)(void *userdata,uint16_t addr,uint8_t value);
+
+struct Bus6502 {
     Memory memory;
     uint8_t keyboard;
     uint32_t rng_state;
     bool easy6502_io;
     bool framebuffer_dirty;
-} Bus6502;
+    bus_read_hook_t read_hook;
+    bus_write_hook_t write_hook;
+    void *hook_userdata;
+};
 
 void bus_init(Bus6502 *bus);
 uint8_t bus_read(Bus6502 *bus, uint16_t addr);
@@ -20,5 +27,7 @@ uint16_t bus_read16(Bus6502 *bus, uint16_t addr);
 void bus_write16(Bus6502 *bus, uint16_t addr, uint16_t value);
 void bus_set_keyboard(Bus6502 *bus, uint8_t key);
 void bus_seed_rng(Bus6502 *bus, uint32_t seed);
+void bus_set_hooks(Bus6502 *bus,bus_read_hook_t read_hook,
+                   bus_write_hook_t write_hook,void *userdata);
 
 #endif