Add etcd_feature_gates and restore the etcd 3.5 flag names (#13569)

Signed-off-by: Ali Afsharzadeh <afsharzadeh8@gmail.com>

roles/etcd_defaults/defaults/main.yml

@@ -117,6 +117,11 @@ etcd_retries: 4
 # Rendered as the InitialCorruptCheck feature gate (etcd 3.6+)
 etcd_experimental_initial_corrupt_check: true
 
+## Feature gates for etcd 3.6 and later, added to InitialCorruptCheck, formatted like:
+##  etcd_feature_gates:
+##    CompactHashCheck: true
+etcd_feature_gates: {}
+
 # Enable distributed tracing
 # https://etcd.io/docs/v3.5/op-guide/monitoring/#distributed-tracing
 etcd_experimental_enable_distributed_tracing: false