Python 3.13 support

[iherasymenko]

When trying to install ddtrace-py with the latest Python 3.13 RC builds, the installation fails with the following error.

building 'ddtrace.profiling.collector._memalloc' extension
creating build/temp.linux-aarch64-cpython-313/ddtrace/profiling/collector
gcc -fno-strict-overflow -Wsign-compare -DNDEBUG -g -O3 -Wall -fPIC -I/tmp/tmperfe434l/.venv/include -I/usr/local/include/python3.13 -c ddtrace/profiling/collector/_memalloc.c -o build/temp.linux-aarch64-cpython-313/ddtrace/profiling/collector/_memalloc.o
gcc -fno-strict-overflow -Wsign-compare -DNDEBUG -g -O3 -Wall -fPIC -I/tmp/tmperfe434l/.venv/include -I/usr/local/include/python3.13 -c ddtrace/profiling/collector/_memalloc_heap.c -o build/temp.linux-aarch64-cpython-313/ddtrace/profiling/collector/_memalloc_heap.o
gcc -fno-strict-overflow -Wsign-compare -DNDEBUG -g -O3 -Wall -fPIC -I/tmp/tmperfe434l/.venv/include -I/usr/local/include/python3.13 -c ddtrace/profiling/collector/_memalloc_tb.c -o build/temp.linux-aarch64-cpython-313/ddtrace/profiling/collector/_memalloc_tb.o
gcc -shared build/temp.linux-aarch64-cpython-313/ddtrace/profiling/collector/_memalloc.o build/temp.linux-aarch64-cpython-313/ddtrace/profiling/collector/_memalloc_heap.o build/temp.linux-aarch64-cpython-313/ddtrace/profiling/collector/_memalloc_tb.o -L/usr/local/lib -o build/lib.linux-aarch64-cpython-313/ddtrace/profiling/collector/_memalloc.cpython-313-aarch64-linux-gnu.so
building 'ddtrace.internal._threads' extension
creating build/temp.linux-aarch64-cpython-313/ddtrace/internal
g++ -fno-strict-overflow -Wsign-compare -DNDEBUG -g -O3 -Wall -fPIC -I/tmp/tmperfe434l/.venv/include -I/usr/local/include/python3.13 -c ddtrace/internal/_threads.cpp -o build/temp.linux-aarch64-cpython-313/ddtrace/internal/_threads.o -std=c++17 -Wall -Wextra
ddtrace/internal/_threads.cpp: In constructor ‘GILGuard::GILGuard()’:
ddtrace/internal/_threads.cpp:23:14: error: ‘_Py_IsFinalizing’ was not declared in this scope; did you mean ‘Py_IsFinalizing’?
   23 |         if (!_Py_IsFinalizing())
      |              ^~~~~~~~~~~~~~~~
      |              Py_IsFinalizing
ddtrace/internal/_threads.cpp: In constructor ‘AllowThreads::AllowThreads()’:
ddtrace/internal/_threads.cpp:45:14: error: ‘_Py_IsFinalizing’ was not declared in this scope; did you mean ‘Py_IsFinalizing’?
   45 |         if (!_Py_IsFinalizing())
      |              ^~~~~~~~~~~~~~~~
      |              Py_IsFinalizing
ddtrace/internal/_threads.cpp: In destructor ‘AllowThreads::~AllowThreads()’:
ddtrace/internal/_threads.cpp:50:14: error: ‘_Py_IsFinalizing’ was not declared in this scope; did you mean ‘Py_IsFinalizing’?
   50 |         if (!_Py_IsFinalizing())
      |              ^~~~~~~~~~~~~~~~
      |              Py_IsFinalizing