BUG/MINOR: mux-h2/stats: make stream/connection proto errors more accurate

BUG/MINOR: mux-h2/stats: make stream/connection proto errors more accurate

Since commit a8879238c ("MINOR: mux-h2: report detected error on stats")
we now have some error stats on stream/connection level protocol errors,
but some were improperly marked as stream while they're connection, and
2 or 3 relevant ones were missing and have now been added.

This could be backported to 2.3.

(cherry picked from commit a307528fe287f085705ef08a798c1698e474c395)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>