[Python o11y] Fix python distribtests (#33365)

Fix for Cython build issue in aarch64.

We're seeing this error in aarch64 distribution test:
```
In file included from ./src/core/lib/slice/slice.h:36,
                 from ./src/core/lib/slice/slice_buffer.h:29,
                 from ./src/core/lib/transport/transport.h:60,
                 from ./src/core/lib/channel/channel_stack.h:75,
                 from ./src/core/lib/channel/call_tracer.h:32,
                 from src/python/grpcio/grpc/_cython/cygrpc.cpp:2230:
./src/core/lib/slice/slice_refcount.h: In member function 'void grpc_slice_refcount::Ref(grpc_core::DebugLocation)':
./src/core/lib/slice/slice_refcount.h:55:25: error: expected ')' before 'PRIdPTR'
               "REF %p %" PRIdPTR "->%" PRIdPTR, this, prev_refs, prev_refs + 1);
                         ^~~~~~~~
                         )
```

Based on [this
post](https://stackoverflow.com/questions/26182336/priuptr-preprocessor-bug-in-gcc),
it's caused by including `<inttypes.h>` before define
`__STDC_FORMAT_MACROS` marco.

`<inttypes.h>` was included in `core/lib/channel/call_tracer.h` and this
macro should already be defined in `grpc/grpc.h` through
`port_platform.h`, but we're still having issue in aarch64, so we
manually define the macro in this PR.

setup.py

@@ -417,6 +417,15 @@ else:
 # TODO(vigneshbabu): Remove this once the poll poller gets fork support.
 DEFINE_MACROS += (('GRPC_DO_NOT_INSTANTIATE_POSIX_POLLER', 1),)
 
+# Fix for Cython build issue in aarch64.
+# It's required to define this macro before include <inttypes.h>.
+# <inttypes.h> was included in core/lib/channel/call_tracer.h.
+# This macro should already be defined in grpc/grpc.h through port_platform.h,
+# but we're still having issue in aarch64, so we manually define the macro here.
+# TODO(xuanwn): Figure out what's going on in the aarch64 build so we can support
+# gcc + Bazel.
+DEFINE_MACROS += (('__STDC_FORMAT_MACROS', None),)
+
 LDFLAGS = tuple(EXTRA_LINK_ARGS)
 CFLAGS = tuple(EXTRA_COMPILE_ARGS)
 if "linux" in sys.platform or "darwin" in sys.platform: