http2: do not update progress on END_STREAM without END_HEADERS

As more continuation frames are expected.
Next commit will update progress for those continuation frames.

Ticket: 9217

Backport note: Gate the existing 8.0.x transaction-state transition on
END_HEADERS for HEADERS frames, preserving DATA and half-closed handling
instead of importing main's per-direction progress state machines.

(cherry picked from commit ef7184012a)

rust/src/http2/http2.rs

@@ -432,7 +432,10 @@ impl HTTP2Transaction {
         //handle closing state changes
         match data {
             HTTP2FrameTypeData::HEADERS(_) | HTTP2FrameTypeData::DATA => {
-                if header.flags & parser::HTTP2_FLAG_HEADER_EOS != 0 {
+                if header.flags & parser::HTTP2_FLAG_HEADER_EOS != 0
+                    && (!matches!(data, HTTP2FrameTypeData::HEADERS(_))
+                        || header.flags & parser::HTTP2_FLAG_HEADER_END_HEADERS != 0)
+                {
                     match self.state {
                         HTTP2TransactionState::HTTP2StateHalfClosedClient
                         | HTTP2TransactionState::HTTP2StateDataServer => {