[clang][ARM] Add a warning for calling an `__attribute__((interrupt))` function

[chrisnc]

#91870 fixes a warning that's existed for a while for bare-metal Arm targets which encourages calling interrupt handlers from other interrupt handlers. Doing this leads to unpredictable behavior and/or infinite loops due to how Arm exception returns are defined: #91870 (comment). clang should instead warn when you try to call an interrupt handler from anywhere.