Update getting pushrules, add tests, tweak pushrules (#2705)

This PR
- adds tests for `evaluatePushrules`
- removes the need for the UserAPI on the `OutputStreamEventConsumer`
(for easier testing)
- adds a method to get the pushrules from the database
- adds a new default pushrule for `m.reaction` events (and some other
tweaks)

internal/pushrules/default_content.go

@@ -16,6 +16,12 @@ func mRuleContainsUserNameDefinition(localpart string) *Rule {
 		Default: true,
 		Enabled: true,
 		Pattern: localpart,
+		Conditions: []*Condition{
+			{
+				Kind: EventMatchCondition,
+				Key:  "content.body",
+			},
+		},
 		Actions: []*Action{
 			{Kind: NotifyAction},
 			{