Better handle explicit chunked encoding responses #12553

Job	Run time
x86_64-gnu-test-preview_mt	5m 41s
check_format	1m 35s
x86_64-gnu-test (1.7.3)	35m 24s
x86_64-musl-test	38m 5s
x86_64-gnu-test (1.8.2)	34m 9s
x86_64-gnu-test (1.9.2)	38m 13s
x86_64-gnu-test (1.10.1)	33m 44s
x86_64-gnu-test (1.11.2)	36m 27s
x86_64-gnu-test (1.12.2)	35m 29s
x86_64-gnu-test (1.13.3)	34m 44s
x86_64-gnu-test (1.14.0)	33m 40s
x86_64-gnu-test (1.0.0, FLAGS=-Dwithout_ffi USE_PCRE1=true)	32m 53s
x86_64-gnu-test (1.1.1, FLAGS=-Dwithout_ffi USE_PCRE1=true)	35m 46s
x86_64-gnu-test (1.2.2, USE_PCRE1=true)	34m 30s
x86_64-gnu-test (1.3.2, USE_PCRE1=true)	33m 51s
x86_64-gnu-test (1.4.1, USE_PCRE1=true)	34m 10s
x86_64-gnu-test (1.5.1, USE_PCRE1=true)	34m 54s
x86_64-gnu-test (1.6.2, USE_PCRE1=true)	37m 55s
	9h 31m 10s

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