Added `slackb.com` SNI. (#2067) #2884

Job	Run time
Python Bindings (ubuntu-latest)	1m 25s
Test Utils (ubuntu-latest)	2m 38s
ubuntu-latest x86_64 --with-local-libgcrypt cc	10m 44s
ubuntu-latest x86_64 cc	8m 1s
ubuntu-20.04 x86_64 --with-local-libgcrypt cc	11m 29s
ubuntu-20.04 x86_64 cc	8m 36s
macOS-latest x86_64 --with-local-libgcrypt cc	6m 4s
macOS-latest x86_64 cc	7m 21s
macos-11 x86_64 --with-local-libgcrypt cc	8m 27s
macos-11 x86_64 cc	6m 38s
windows-latest x86_64 --with-local-libgcrypt cc	32m 24s
windows-latest x86_64 cc	12m 6s
ubuntu-20.04 x86_64 gcc-7 --with-pcre --with-maxminddb --with-sanitizer	16m 17s
ubuntu-22.04 x86_64 gcc-12 --with-pcre --with-maxminddb --with-sanitizer --with-lto-and-gold-linker	33m 32s
ubuntu-20.04 x86_64 clang-7 --with-pcre --with-maxminddb --with-sanitizer	24m 27s
ubuntu-22.04 x86_64 clang-14 --with-pcre --with-maxminddb --with-sanitizer --with-lto-and-gold-linker	36m 43s
ubuntu-latest x86_64 cc --with-pcre --with-maxminddb --with-thread-sanitizer	53m 15s
ubuntu-latest x86_64 cc --with-pcre --with-maxminddb --with-sanitizer nBPF	20m 1s
ubuntu-22.04 x86_64 clang-14 --with-pcre --with-maxminddb --with-memory-sanitizer	1h 20m 33s
macOS-latest x86_64 cc --with-pcre --with-maxminddb	6m 49s
macos-12 x86_64 cc --with-pcre --with-maxminddb	6m 54s
ubuntu-latest arm64 cc --with-pcre --with-maxminddb	29m 35s
ubuntu-latest armhf cc --with-pcre --with-maxminddb --with-sanitizer	2h 9m 57s
ubuntu-latest s390x cc --with-pcre --with-maxminddb	34m 11s
	9h 48m 7s

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