moq_decode: request_id left response messages in draft-17, not 18

Per the draft-17 spec text, Request ID was already removed from
PUBLISH_DONE, SUBSCRIBE_OK, REQUEST_OK, REQUEST_ERROR and FETCH_OK in
draft-17 (implicit from the bidi request stream context). The tool's
gates said draft < 18, copied from MoQFramer -- but moxygen skips
draft 17 entirely (kSupportedVersions = 14/15/16/18), so its < 18
gates are only ever exercised as <= 16 and happen to work. For a
spec decoder with an explicit --version flag, < 17 is the correct
boundary.

Fixes:
- PUBLISH_DONE and FETCH_OK read request_id unconditionally; gate them.
- SUBSCRIBE_OK / REQUEST_OK / REQUEST_ERROR gates corrected 18 -> 17.

Reported by a user decoding draft-17 PUBLISH_DONE frames.

Author: gmarzot

tools/moq_decode.py

@@ -517,8 +517,8 @@ def parse_subscribe(cursor, annot, draft, payload_end=None):
 
 
 def parse_subscribe_ok(cursor, annot, draft, payload_end):
-    # Draft 18+: request_id is implicit from the bidi request stream context.
-    if draft < 18:
+    # Draft 17+: request_id is implicit from the bidi request stream context.
+    if draft < 17:
         val, s = cursor.read_varint()
         annot.add(s, cursor.pos, "request_id", str(val))
     val, s = cursor.read_varint()
@@ -545,9 +545,9 @@ def parse_subscribe_ok(cursor, annot, draft, payload_end):
 
 
 def parse_request_error(cursor, annot, draft, payload_end):
-    # Draft 18+: request_id is implicit from the bidi request stream context;
+    # Draft 17+: request_id is implicit from the bidi request stream context;
     # the receiver FIFO-correlates errors with outstanding requests.
-    if draft < 18:
+    if draft < 17:
         val, s = cursor.read_varint()
         annot.add(s, cursor.pos, "request_id", str(val))
     val, s = cursor.read_varint()
@@ -569,8 +569,8 @@ def parse_publish_namespace(cursor, annot, draft, payload_end):
 
 
 def parse_request_ok(cursor, annot, draft, payload_end):
-    # Draft 18+: request_id is implicit (per-stream).
-    if draft < 18:
+    # Draft 17+: request_id is implicit (per-stream).
+    if draft < 17:
         val, s = cursor.read_varint()
         annot.add(s, cursor.pos, "request_id", str(val))
     if draft > 14:
@@ -610,8 +610,10 @@ def parse_unsubscribe(cursor, annot, draft, payload_end):
 
 
 def parse_publish_done(cursor, annot, draft, payload_end):
-    val, s = cursor.read_varint()
-    annot.add(s, cursor.pos, "request_id", str(val))
+    # Draft 17+: request_id is implicit from the bidi request stream context.
+    if draft < 17:
+        val, s = cursor.read_varint()
+        annot.add(s, cursor.pos, "request_id", str(val))
     val, s = cursor.read_varint()
     annot.add(s, cursor.pos, "status_code", str(val))
     val, s = cursor.read_varint()
@@ -777,8 +779,10 @@ def parse_fetch_cancel(cursor, annot, draft, payload_end):
 
 
 def parse_fetch_ok(cursor, annot, draft, payload_end):
-    val, s = cursor.read_varint()
-    annot.add(s, cursor.pos, "request_id", str(val))
+    # Draft 17+: request_id is implicit from the bidi request stream context.
+    if draft < 17:
+        val, s = cursor.read_varint()
+        annot.add(s, cursor.pos, "request_id", str(val))
 
     if draft < 15:
         val, s = cursor.read_uint8()