[FR] Standardize on how to enable optional bltouch

### Bug Description

It present there are two different ways to do this board name _USE_BLTOUCH or _BLTOUCH

examples

config/examples/BIQU/B1/Configuration.h://#define B1_USE_BLTOUCH // Uncomment for BLTouch support
config/examples/Two Trees/Sapphire Plus/Sapphire Plus V2.1/Configuration.h://#define SAPPHIRE_PLUS_BLTOUCH
config/examples/Two Trees/Sapphire Plus/Sapphire Plus V2/Configuration.h://#define SAPPHIRE_PLUS_BLTOUCH
config/examples/Two Trees/BlueR/BlueR V3/Configuration.h://#define BLUER_BLTOUCH // Enable if you want to use BLTOUCH
config/examples/Two Trees/BlueR/BlueR V1/Configuration.h://#define BLUER_BLTOUCH // Enable if you want to use BLTOUCH
config/examples/Two Trees/BlueR/BlueR V2/Configuration.h://#define BLUER_BLTOUCH // Enable if you want to use BLTOUCH
config/examples/Two Trees/Sapphire Pro/Configuration.h://#define SPRO_BLTOUCH // Enable if you want to use BLTOUCH
config/examples/Eryone/Thinker SE/Configuration.h://#define THINKERV2_BLTOUCH // Enable for an installed BLTOUCH
config/examples/Eryone/Thinker SE/README.md: `//#define THINKERV2_BLTOUCH // Enable for an installed BLTOUCH`
config/examples/Eryone/Thinker V2/Configuration.h://#define THINKERV2_BLTOUCH // Enable for an installed BLTOUCH
config/examples/Eryone/Thinker V2/README.md: `//#define THINKERV2_BLTOUCH // Enable for an installed BLTOUCH`
config/examples/AnyCubic/i3 Mega/Trigorilla AVR/Configuration.h://#define I3MEGA_HAS_BLTOUCH
config/examples/AnyCubic/i3 Mega/Trigorilla Pro STM32/Configuration.h://#define I3MEGA_HAS_BLTOUCH
config/examples/Kingroon/KP3S_Pro/Configuration.h://#define USE_BLTOUCH
config/examples/Creality/Ender-5 Pro/CrealityV422/Configuration.h://#define ENDER5_USE_BLTOUCH
config/examples/Creality/Ender-5 Pro/BigTreeTech SKR E3 Turbo/Configuration.h://#define E5_USE_BLTOUCH
config/examples/Creality/Ender-6/Configuration.h://#define E6_USE_BLTOUCH
config/examples/Creality/CR-10 V3/Configuration.h://#define CR10V3_BLTOUCH
config/examples/Creality/CR-10 V2/Configuration.h:#define CR10V2_BLTOUCH

**Expected behavior:**

All follow a standard implmentation

**Actual behavior:**

chaos

Start by comparing the BLTouch definitions listed in the configuration/examples/Configuration.h files and the corresponding README.md entries. Determine the project-wide naming convention to apply, then update the affected example configurations and documentation so the optional BLTouch setting is consistent everywhere.

Written by the indexing model from the issue text.