Merge bitcoin/bitcoin#31093: Introduce g_fuzzing global for fuzzing checks

9f243cd7fa Introduce `g_fuzzing` global for fuzzing checks (dergoegge)

Pull request description:

  This PR introduces a global `g_fuzzing` that indicates if we are fuzzing.

  If `g_fuzzing` is `true` then:

  * Assume checks are enabled
  * Special fuzzing paths are taken (e.g. pow check is reduced to one bit)

  Closes #30950 #31057

ACKs for top commit:
  maflcko:
    review ACK 9f243cd7fa 🗜
  brunoerg:
    crACK 9f243cd7fa
  marcofleon:
    Tested ACK 9f243cd7fa

Tree-SHA512: 56e4cad0555dec0c565ea5ecc529628ee4f37d20dc660c647fdc6948fbeed8291e6fe290de514bd4c2c7089654d9ce1add607dc9855462828b62be9ee45e4999

CMakeLists.txt

@@ -234,11 +234,6 @@ if(BUILD_FOR_FUZZING)
   set(BUILD_GUI_TESTS OFF)
   set(BUILD_BENCH OFF)
   set(BUILD_FUZZ_BINARY ON)
-
-  target_compile_definitions(core_interface INTERFACE
-    ABORT_ON_FAILED_ASSUME
-    FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
-  )
 endif()
 
 include(ProcessConfigurations)