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

tests/data/Makefile.inc

@@ -250,7 +250,7 @@ test2400 test2401 test2402 test2403 \
 \
 test2500 test2501 test2502 test2503 \
 \
-test2600 test2601 test2602 \
+test2600 test2601 test2602 test2603 \
 \
 test3000 test3001 test3002 test3003 test3004 test3005 test3006 test3007 \
 test3008 test3009 test3010 test3011 test3012 test3013 test3014 test3015 \

tests/data/test2603

@@ -0,0 +1,22 @@
+<testcase>
+<info>
+<keywords>
+unittest
+http1
+</keywords>
+</info>
+
+#
+# Client-side
+<client>
+<server>
+none
+</server>
+<features>
+unittest
+</features>
+ <name>
+http1 parser unit tests
+ </name>
+</client>
+</testcase>