all: Rename the "NORETURN" macro to "MP_NORETURN".

This commit renames the NORETURN macro, indicating to the compiler
that a function does not return, into MP_NORETURN to maintain the same
naming convention of other similar macros.

To maintain compaitiblity with existing code NORETURN is aliased to
MP_NORETURN, but it is also deprecated for MicroPython v2.

This changeset was created using a similar process to
decf8e6a8b ("all: Remove the "STATIC"
macro and just use "static" instead."), with no documentation or python
scripts to change to reflect the new macro name.

Signed-off-by: Alessandro Gatti <a.gatti@frob.it>

shared/libc/abort_.c

@@ -1,7 +1,7 @@
 #include <py/runtime.h>
 
-NORETURN void abort_(void);
+MP_NORETURN void abort_(void);
 
-NORETURN void abort_(void) {
+MP_NORETURN void abort_(void) {
     mp_raise_msg(&mp_type_RuntimeError, MP_ERROR_TEXT("abort() called"));
 }