Tests for resp_hdr_add and resp_hdr_set

[const-t]

Need to develop more tests for directives resp_hdr_set and resp_hdr_add.

Tests must include:

• [x] Testing of resp_hdr_set and resp_hdr_add for special(singular-nonsingular) and raw headers.
• [x] Testing of small and large(10+kb) headers.
• [x] Testing of header deletion using resp_hdr_set.
• [x] Testing of multiple same directives in vhost.
• [x] Testing of hpack static table.
• [x] Testing of appending value to existed header for http1(http2 doesn't have this).
• [x] Test of multiple appending to same header.
• [x] Test hpack dynamic table and resp_hdr_add version of this test.
• [x] Each test must have version for both protocols http1 and http2.
• [x] As well must have version with enabled caching for both protocols.