[TEST] Bound the curl cases, and check the layout claim instead of asserting it

Two things this branch said but did not enforce.

The cases here cover waits that are meant to end. When one stops ending
it hangs rather than fails, and nothing bounded them, so a regression
took the whole job with it instead of reporting. That happened three
times while this branch was being written, each time as exit 124 with no
case after it running. Every curl case now carries a CTest timeout of
120 seconds, read back from ctest --show-only=json-v1 as 120.0 on all
35. The slowest case that legitimately waits takes thirty.

The description also claimed that std::atomic<SessionState> is one byte,
aligned to one, and lock free, so the installed layout does not move.
That was a measurement on one toolchain stated as a property of the
language. The standard promises none of it. The size and alignment
halves are now static_asserts, so a toolchain where they do not hold
says so while building rather than silently changing an installed type.

32 tests pass.

Signed-off-by: thc1006 <84045975+thc1006@users.noreply.github.com>

Author: thc1006

ext/src/http/client/curl/http_operation_curl.cc

@@ -401,6 +401,18 @@ int HttpOperation::OnProgressCallback(void *clientp,
 }
 #endif
 
+// The atomic member is only free of layout cost while it stays the size and alignment of the
+// enum it replaced. The standard does not promise that, so it is checked here rather than
+// asserted in prose: a toolchain where it does not hold changes an installed type and should say
+// so at build time.
+static_assert(sizeof(std::atomic<opentelemetry::ext::http::client::SessionState>) ==
+                  sizeof(opentelemetry::ext::http::client::SessionState),
+              "std::atomic<SessionState> grew, which changes the layout of HttpOperation");
+static_assert(
+    alignof(std::atomic<opentelemetry::ext::http::client::SessionState>) ==
+        alignof(opentelemetry::ext::http::client::SessionState),
+    "std::atomic<SessionState> is more aligned, which changes the layout of HttpOperation");
+
 void HttpOperation::DispatchEvent(opentelemetry::ext::http::client::SessionState type,
                                   const std::string &reason)
 {

ext/test/http/CMakeLists.txt

@@ -15,6 +15,11 @@ if(WITH_HTTP_CLIENT_CURL)
     TARGET ${FILENAME}
     TEST_PREFIX ext.http.curl.
     TEST_LIST ${FILENAME})
+  # These cover waits that are meant to end. When one stops ending it hangs
+  # rather than fails, and without a bound it takes the whole job with it
+  # instead of reporting. The slowest case that legitimately waits takes thirty
+  # seconds.
+  set_tests_properties(${${FILENAME}} PROPERTIES TIMEOUT 120)
 endif()
 
 set(SOCKET_TOOLS_FILENAME socket_tools_test)