Extensible split data sync (#11930)

* Extensible split data sync capability through transactions.

- Split common transport has been split up between the transport layer
  and data layer.
- Split "transactions" model used, with convergence between I2C and
  serial data definitions.
- Slave matrix "generation count" is used to determine if the full slave
  matrix needs to be retrieved.
- Encoders get the same "generation count" treatment.
- All other blocks of data are synchronised when a change is detected.
- All transmissions have a globally-configurable deadline before a
  transmission is forced (`FORCED_SYNC_THROTTLE_MS`, default 100ms).
- Added atomicity for all core-synced data, preventing partial updates
- Added retries to AVR i2c_master's i2c_start, to minimise the number of
  failed transactions when interrupts are disabled on the slave due to
  atomicity checks.
- Some keyboards have had slight modifications made in order to ensure
  that they still build due to firmware size restrictions.

* Fixup LED_MATRIX compile.

* Parameterise ERROR_DISCONNECT_COUNT.

quantum/split_common/matrix.c

@@ -23,9 +23,11 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include "quantum.h"
 #include "split_util.h"
 #include "config.h"
-#include "transport.h"
+#include "transactions.h"
 
-#define ERROR_DISCONNECT_COUNT 5
+#ifndef ERROR_DISCONNECT_COUNT
+#    define ERROR_DISCONNECT_COUNT 5
+#endif  // ERROR_DISCONNECT_COUNT
 
 #define ROWS_PER_HAND (MATRIX_ROWS / 2)