Rework bcat Crkbd and Lily58 modifier keys (#9692)

* Re-enable mouse keys to fix Chrome OS media keys

I'm not sure if there's a bug in Chrome OS, QMK, or both, but
EXTRAKEY_ENABLE isn't sufficient for media keys to work on Chrome OS.
Instead, MOUSEKEY_ENABLE is also required.

* Remove unnecessary SPLIT_USB_DETECT for Lily58

I've since swapped my Lily58 back to Elite-C v2 controllers with working
VBUS detection.

* Move Crkbd Esc and Ctrl keys; add some shortcuts

* Move MC_ALTT to userspace for cross-board support

* Sync Lily58 keymap with Crkbd

* Fix typos

users/bcat/rules.mk

@@ -3,8 +3,10 @@ SRC += bcat.c
 # Enable Bootmagic Lite to consistently reset to bootloader and clear EEPROM.
 BOOTMAGIC_ENABLE = lite
 
-# Enable media keys on all keyboards.
+# Enable media keys on all keyboards. (Even though I don't use mouse keys, they
+# seem to be required for media keys to register on Chrome OS.)
 EXTRAKEY_ENABLE = yes
+MOUSEKEY_ENABLE = yes
 
 # Enable link-time optimization to reduce binary size.
 LINK_TIME_OPTIMIZATION_ENABLE = yes
@@ -12,7 +14,6 @@ LINK_TIME_OPTIMIZATION_ENABLE = yes
 # Disable unused build options on all keyboards.
 COMMAND_ENABLE = no
 CONSOLE_ENABLE = no
-MOUSEKEY_ENABLE = no
 NKRO_ENABLE = no
 TERMINAL_ENABLE = no