add EMA as mode to SSLChannels #1043

Job	Run time
build_windows (windows-latest, 3.9)	1m 18s
build_windows (windows-latest, 3.10)	1m 30s
build (ubuntu-20.04, 3.9)	1m 27s
build_windows (windows-latest, 3.11)	1m 16s
build (ubuntu-20.04, 3.10)	1m 27s
build (ubuntu-20.04, 3.11)	1m 27s
build_windows (windows-latest, 3.12)	1m 26s
build (ubuntu-20.04, 3.12)	1m 40s
build (ubuntu-22.04, 3.9)	1m 27s
build (ubuntu-22.04, 3.10)	1m 24s
build (ubuntu-22.04, 3.11)	1m 24s
build (ubuntu-22.04, 3.12)	1m 31s
build (macos-12, 3.9)	1m 24s
build (macos-12, 3.10)	1m 32s
build (macos-12, 3.11)	2m 7s
build (macos-12, 3.12)	2m 9s
build (macos-13, 3.9)	1m 56s
build (macos-13, 3.10)	1m 20s
build (macos-13, 3.11)	1m 49s
build (macos-13, 3.12)	1m 57s
build (macos-14, 3.10)	1m 4s
build (macos-14, 3.11)	59s
build (macos-14, 3.12)	1m 2s
notify-complete	4s
deploy	0s
	34m 40s

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