test/pytest_suite: fix more tests broken by httpx auto-decompression

test/pytest_suite: fix more tests broken by httpx auto-decompression

httpx transparently inflates gzip/deflate response bodies (it keeps the
Content-Encoding header but .content/.text are the decoded plaintext). Three
more tests asserted on the body of a compressed response and so were wrong:

  - pr43939 / pr17629: re-POSTed r.content (decoded plaintext, not the gzip
    stream) through the inflate input filter -- same round-trip bug as
    pr49328/deflate.
  - reflector: 'assert r.text != payload' could never hold, since httpx
    decoded the gzip body straight back to the payload.

Generalise the GET_RAW helper into a raw_response(method, path, ...) that
streams the response, reads iter_raw() (undecoded bytes), and stashes them on
.raw_content while leaving .status_code/.headers intact -- so tests can assert
on both the raw body and the headers. GET_RAW now delegates to it; update the
three tests to use raw_response/.raw_content.

The length-based tests (rwrite, passbrigade, getfile, byterange7) are
unaffected: they measure len(.content) after decoding, which equals the
original length regardless of transfer compression.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1934950 13f79535-47bb-0310-9956-ffa450edef68