gh-93649: Split unicode tests from _testcapimodule.c & add some more (GH-95819)

- Move PyUnicode tests to a separate file
- Add some more tests for PyUnicode_FromFormat

Co-authored-by: philg314 <[email protected]>

Author: encukou

Misc/ACKS

@@ -609,6 +609,7 @@ Jan-Philip Gehrcke
 Thomas Gellekum
 Gabriel Genellina
 Christos Georgiou
+Philip Georgi
 Elazar (אלעזר) Gershuni
 Ben Gertzfield
 Nadim Ghaznavi

Modules/Setup.stdlib.in

@@ -169,7 +169,7 @@
 @MODULE__XXTESTFUZZ_TRUE@_xxtestfuzz _xxtestfuzz/_xxtestfuzz.c _xxtestfuzz/fuzzer.c
 @MODULE__TESTBUFFER_TRUE@_testbuffer _testbuffer.c
 @MODULE__TESTINTERNALCAPI_TRUE@_testinternalcapi _testinternalcapi.c
-@MODULE__TESTCAPI_TRUE@_testcapi _testcapimodule.c _testcapi/vectorcall.c _testcapi/vectorcall_limited.c _testcapi/heaptype.c
+@MODULE__TESTCAPI_TRUE@_testcapi _testcapimodule.c _testcapi/vectorcall.c _testcapi/vectorcall_limited.c _testcapi/heaptype.c _testcapi/unicode.c
 
 # Some testing modules MUST be built as shared libraries.
 *shared*

Modules/_testcapi/parts.h

@@ -3,3 +3,4 @@
 int _PyTestCapi_Init_Vectorcall(PyObject *module);
 int _PyTestCapi_Init_VectorcallLimited(PyObject *module);
 int _PyTestCapi_Init_Heaptype(PyObject *module);
+int _PyTestCapi_Init_Unicode(PyObject *module);