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.

keyboards/draculad/config.h

@@ -65,3 +65,5 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #define UNUSED_PINS
 
 #define EE_HANDS
+
+#define LAYER_STATE_8BIT

keyboards/handwired/freoduo/rules.mk

@@ -11,7 +11,7 @@ BOOTMAGIC_ENABLE = no       # Virtual DIP switch configuration
 MOUSEKEY_ENABLE = yes       # Mouse keys
 EXTRAKEY_ENABLE = yes       # Audio control and System control
 CONSOLE_ENABLE = no         # Console for debug
-COMMAND_ENABLE = yes        # Commands for debug and configuration
+COMMAND_ENABLE = no         # Commands for debug and configuration
 # Do not enable SLEEP_LED_ENABLE. it uses the same timer as BACKLIGHT_ENABLE
 SLEEP_LED_ENABLE = no       # Breathing sleep LED during USB suspend
 # if this doesn't work, see here: https://github.com/tmk/tmk_keyboard/wiki/FAQ#nkro-doesnt-work
@@ -21,4 +21,4 @@ RGBLIGHT_ENABLE = yes       # Enable keyboard RGB underglow
 BLUETOOTH_ENABLE = no       # Enable Bluetooth
 AUDIO_ENABLE = no           # Audio output
 VELOCIKEY_ENABLE = yes
-SPLIT_KEYBOARD = yes
+SPLIT_KEYBOARD = yes

keyboards/helix/rev2/keymaps/default/rules.mk

@@ -5,7 +5,7 @@
 #   See TOP/keyboards/helix/rules.mk for a list of options that can be set.
 #   See TOP/docs/config_options.md for more information.
 #
-LTO_ENABLE = no  # if firmware size over limit, try this option
+LTO_ENABLE = yes  # if firmware size over limit, try this option
 
 # Helix Spacific Build Options
 # you can uncomment and edit follows 7 Variables

keyboards/keebio/iris/rev2/rules.mk

@@ -32,3 +32,5 @@ RGBLIGHT_ENABLE = yes       # Enable WS2812 RGB underlight.
 SLEEP_LED_ENABLE = no    # Breathing sleep LED during USB suspend
 
 SPLIT_KEYBOARD = yes
+
+LTO_ENABLE = yes

keyboards/keebio/iris/rev3/rules.mk

@@ -33,3 +33,4 @@ SLEEP_LED_ENABLE = no    # Breathing sleep LED during USB suspend
 
 SPLIT_KEYBOARD = yes
 ENCODER_ENABLE = yes
+LTO_ENABLE = yes

keyboards/keebio/iris/rev4/rules.mk

@@ -33,3 +33,5 @@ SLEEP_LED_ENABLE = no    # Breathing sleep LED during USB suspend
 
 SPLIT_KEYBOARD = yes
 ENCODER_ENABLE = yes
+
+LTO_ENABLE = yes

keyboards/keebio/quefrency/rules.mk

@@ -19,3 +19,4 @@ SLEEP_LED_ENABLE = no    # Breathing sleep LED during USB suspend
 SPLIT_KEYBOARD = yes
 
 DEFAULT_FOLDER = keebio/quefrency/rev1
+LTO_ENABLE = yes

keyboards/keebio/viterbi/rev2/rules.mk

@@ -1,3 +1,5 @@
 BACKLIGHT_ENABLE = yes
 
 LAYOUTS = ortho_5x14
+
+LTO_ENABLE = yes

keyboards/keebio/viterbi/rules.mk

@@ -19,16 +19,16 @@ BOOTMAGIC_ENABLE = no       # Virtual DIP switch configuration
 MOUSEKEY_ENABLE = yes       # Mouse keys
 EXTRAKEY_ENABLE = yes       # Audio control and System control
 CONSOLE_ENABLE = no         # Console for debug
-COMMAND_ENABLE = yes        # Commands for debug and configuration
+COMMAND_ENABLE = no         # Commands for debug and configuration
 NKRO_ENABLE = no            # Nkey Rollover - if this doesn't work, see here: https://github.com/tmk/tmk_keyboard/wiki/FAQ#nkro-doesnt-work
-BACKLIGHT_ENABLE = no      # Enable keyboard backlight functionality
+BACKLIGHT_ENABLE = no       # Enable keyboard backlight functionality
 MIDI_ENABLE = no            # MIDI controls
 AUDIO_ENABLE = no           # Audio output on port C6
 UNICODE_ENABLE = no         # Unicode
 BLUETOOTH_ENABLE = no       # Enable Bluetooth with the Adafruit EZ-Key HID
-RGBLIGHT_ENABLE = no       # Enable WS2812 RGB underlight.
+RGBLIGHT_ENABLE = no        # Enable WS2812 RGB underlight.
 # Do not enable SLEEP_LED_ENABLE. it uses the same timer as BACKLIGHT_ENABLE
-SLEEP_LED_ENABLE = no    # Breathing sleep LED during USB suspend
+SLEEP_LED_ENABLE = no       # Breathing sleep LED during USB suspend
 
 SPLIT_KEYBOARD = yes