[3.15] gh-150743: Limit trailer lines and interim responses read by http.client ...

[3.15] gh-150743: Limit trailer lines and interim responses read by http.client (GH-150741) (#152523)

gh-150743: Limit trailer lines and interim responses read by http.client (GH-150741)

http.client read chunked-response trailer lines and skipped interim (1xx)
responses in unbounded loops, so a server streaming either forever would
hang the client even with a socket timeout set (data keeps arriving, so
the timeout never fires).

Trailer lines are now limited to max_response_headers (100 by default)
and interim responses to 100; HTTPException is raised past either limit.

Follow-up to gh-88188 for CVE-2021-3737, which bounded header lines
within an interim response but not these two sibling loops.
(cherry picked from commit 41cc78a7a47fe584e2c2899737fec877d61ae331)

Co-authored-by: Gregory P. Smith <68491+gpshead@users.noreply.github.com>
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This issue was reported to us via [GHSA-w4q2-g22w-6fr4](https://github.com/python/cpython/security/advisories/GHSA-w4q2-g22w-6fr4) and was determined not to be high enough severity to handle privately.

Co-authored-by: Gregory P. Smith <68491+gpshead@users.noreply.github.com>