add tests for headers in h2 request

[RomanBelozerov]

We have tests for h2 headers in response, but we also need tests for h2 headers in request. Cases:

• [x] h2 request with capitalized header. issue #1729
• [x] h2 request with 'transfer-encoding: chunked' header. issue #1730
• [x] h2 requests/responses with invalid Content-Length header. See t_wrong_length directory #304.
• [x] h2 requests with invalid 8.1.2.1. Pseudo-Header Fields RFC7540
• [x] h2 requests/responses must not contain connection-specific headers

• [x] h2 request frame header has incorrect frame payload length field. For example, for the following request: |[00 00 05] [01] [05] [00 00 03 7f] [84 87 bf 82 be]| Frame payload length -> 5 Frame type -> HEADERS Frame flags -> END_HEADERS + END_STREAM Stream ID -> 0x7f03 The actual request headers in this order: :path, :scheme, :authority, :method, user-agent:. All the headers are encoded as Indexed Header Field, taking 1 byte each.

  Need to change frame payload length to the value bigger than 5 and see how Tempesta would handle it.