PLT-5308 Caching layer part 2 (#6973)

* Adding Reaction store cache layer example

* Implementing reaction store in new caching system.

* Redis for reaction store

* Adding redis library

* Adding invalidation for DeleteAllWithEmojiName and other minor enhancements

vendor/github.com/go-redis/redis/Makefile

@@ -0,0 +1,19 @@
+all: testdeps
+	go test ./...
+	go test ./... -short -race
+	go vet
+
+testdeps: testdata/redis/src/redis-server
+
+bench: testdeps
+	go test ./... -test.run=NONE -test.bench=. -test.benchmem
+
+.PHONY: all test testdeps bench
+
+testdata/redis:
+	mkdir -p $@
+	wget -qO- https://github.com/antirez/redis/archive/unstable.tar.gz | tar xvz --strip-components=1 -C $@
+
+testdata/redis/src/redis-server: testdata/redis
+	sed -i 's/libjemalloc.a/libjemalloc.a -lrt/g' $</src/Makefile
+	cd $< && make all