http2: add writableObjectMode and writableNeedDrain getters to Http2ServerResponse #6089

Job	Run time
Build slim tarball	2m 47s
collect-openssl-versions	11s
aarch64-linux: Cache V8 build	6s
aarch64-darwin: with shared libraries	22m 9s
x86_64-darwin: with shared libraries	44m 12s
x86_64-linux: with shared libraries	24m 15s
aarch64-linux: with shared openssl_3_6 (3.6.1)	23m 38s
aarch64-linux: with shared openssl_3 (3.0.19)	23m 55s
aarch64-linux: with shared openssl_3_5 (3.5.5)	23m 54s
aarch64-linux: with shared openssl_4_0 (4.0.0)	23m 40s
aarch64-linux: with shared openssl_1_1 (1.1.1w)	23m 37s
	3h 32m 24s

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