http2: support HTTP/2 to forward proxies, non-tunneling

- with `--proxy-http2` allow h2 ALPN negotiation to
  forward proxies
- applies to http: requests against a https: proxy only,
  as https: requests will auto-tunnel
- adding a HTTP/1 request parser in http1.c
- removed h2h3.c
- using new request parser in nghttp2 and all h3 backends
- adding test 2603 for request parser
- adding h2 proxy test cases to test_10_*

scorecard.py: request scoring accidentally always run curl
with '-v'. Removed that, expect double numbers.

labeller: added http1.* and h2-proxy sources to detection

Closes #10967

lib/bufq.c

@@ -142,6 +142,21 @@ static size_t chunk_skip(struct buf_chunk *chunk, size_t amount)
   return n;
 }
 
+static void chunk_shift(struct buf_chunk *chunk)
+{
+  if(chunk->r_offset) {
+    if(!chunk_is_empty(chunk)) {
+      size_t n = chunk->w_offset - chunk->r_offset;
+      memmove(chunk->x.data, chunk->x.data + chunk->r_offset, n);
+      chunk->w_offset -= chunk->r_offset;
+      chunk->r_offset = 0;
+    }
+    else {
+      chunk->r_offset = chunk->w_offset = 0;
+    }
+  }
+}
+
 static void chunk_list_free(struct buf_chunk **anchor)
 {
   struct buf_chunk *chunk;
@@ -479,6 +494,13 @@ void Curl_bufq_skip(struct bufq *q, size_t amount)
   }
 }
 
+void Curl_bufq_skip_and_shift(struct bufq *q, size_t amount)
+{
+  Curl_bufq_skip(q, amount);
+  if(q->tail)
+    chunk_shift(q->tail);
+}
+
 ssize_t Curl_bufq_pass(struct bufq *q, Curl_bufq_writer *writer,
                        void *writer_ctx, CURLcode *err)
 {