Add a QUIC test for back pressure #812

Job	Run time
basic_clang	3m 39s
basic_gcc	4m 50s
check_docs	1m 10s
check_update	1m 42s
check-ansi	3m 50s
minimal	3m 59s
no-deprecated	3m 38s
no-shared (ubuntu-latest)	1s
no-shared (macos-latest)	3m 0s
address_ub_sanitizer	13m 59s
buildtest	3m 46s
enable_brotli_and_asan_ubsan	12m 52s
enable_brotli_and_zstd_dynamic	7m 21s
enable_brotli_dynamic	7m 22s
enable_non-default_options	3m 32s
enable_zstd_and_asan_ubsan	13m 49s
enable_zstd_dynamic	7m 12s
enable-tfo (ubuntu-latest)	1s
enable-tfo (macos-latest)	4m 23s
external-test-cf-quiche	4m 5s
external-test-pyca (1.51.0, 3.9)	11m 23s
external-tests	5m 46s
fips_and_ktls	3m 57s
legacy	5m 42s
memory_sanitizer	18m 38s
no-legacy	3m 54s
non-caching	19m 24s
out-of-source-and-install (ubuntu-latest)	1s
out-of-source-and-install (macos-latest)	5m 5s
threads_sanitizer	5m 4s
	3h 3m 5s

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