Fix for modern cython stdlib 3.1.x for request_context optional.value()

Summary:
In cython 3.1.x optional definition in the cython stdlib changed `.value` to have an except + which causes cython to generate broken c++ "most" of the time.

```
=================================================================
==1176273==ERROR: AddressSanitizer: stack-use-after-scope on address 0x7efd7956ef88 at pc 0x7efd5934d54e bp 0x7ffcf3642b50 sp 0x7ffcf3642b48
READ of size 8 at 0x7efd7956ef88 thread T0
SCARINESS: 23 (8-byte-read-stack-use-after-scope)
    #0 0x7efd5934d54d in std::basic_string_view<char, std::char_traits<char>>::data() const fbcode/third-party-buck/platform010/build/libgcc/include/c++/trunk/string_view:263
    #1 0x7efd5934a17b in __pyx_f_6thrift_6python_11server_impl_15request_context__get_agent_from_metadata[abi:cxx11](std::optional<apache::thrift::ClientMetadataRef>) buck-out/v2/gen/fbcode/a71b5f55c381bd0a/thrift/lib/python/server/__request_context__request_context.cpp__/out/request_context.cpp:21692
```

In c++ this looks like

```
try {
  _pyx_s = Opt.value():
} catch (...) {
}

_pyx_r_s = _pyx_s.value();
```

So since the first optional is not moveable the variable goes out of scope.  and thus address sanitizer has issues.

Reviewed By: itamaro

Differential Revision: D85457795

fbshipit-source-id: 0befb2e2cb4c9efd62c1fdcaa6ba48f7162b7136

Author: fried

third-party/thrift/src/thrift/lib/python/server/request_context.pxd

@@ -15,7 +15,6 @@
 from cpython.ref cimport PyObject
 from libc.stdint cimport uint64_t
 from libcpp cimport bool as cbool
-from libcpp.optional cimport optional
 from libcpp.memory cimport unique_ptr
 from libcpp.string cimport string
 from libcpp.utility cimport pair
@@ -26,6 +25,12 @@ from thrift.python.common cimport cPriority
 from thrift.python.server_impl.event_handler cimport cfollySocketAddress
 from thrift.python.common cimport Headers
 
+# Cython stdlib in 3.1.x has an except+ on the value() which breaks C++ scoping rules.
+cdef extern from "<optional>" namespace "std" nogil:
+    cdef cppclass optional[T]:
+        cbool has_value()
+        T& value()
+
 cdef extern from "folly/container/F14Map.h" namespace "folly":
   cdef cppclass F14NodeMap[K, T]:
     cppclass const_iterator: