Code Cleanup: unused includes, useless checks, unused variables, etc... (#3696)

* Remove unnecessary checks
* Sublime: never insert missing headers
* Cleanup furi defines use
* Cleanup startup. Cleanup linker scripts. Explicitly define all interrupts hadlers, including uninmplemented one.
* Startup routine in C
* Drop assembler startup
* Move linker defines to stm32wb55_linker.h, cleanup naming, unify usage. Mpu: protect last 32b of main stack. Document various obscure things.
* Move furi_hal_switch documentation to appropriate place, use 0x0 for updater jump.
* UnitTests: move all temporary test files into tmp folder

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Co-authored-by: SG <who.just.the.doctor@gmail.com>

targets/f7/furi_hal/furi_hal_flash.c

@@ -8,6 +8,7 @@
 
 #include <stm32wbxx.h>
 #include <stm32wbxx_ll_hsem.h>
+#include <stm32wb55_linker.h>
 
 #include <hsem_map.h>
 
@@ -53,9 +54,6 @@
     (((__VALUE__) >= FLASH_BASE) && ((__VALUE__) <= (FLASH_BASE + FLASH_SIZE - 8UL)) && \
      (((__VALUE__) % 8UL) == 0UL))
 
-/* Free flash space borders, exported by linker */
-extern const void __free_flash_start__;
-
 size_t furi_hal_flash_get_base(void) {
     return FLASH_BASE;
 }