MM-10020: avoid duplicating unique indexes (#8587)

* unit test TestGet(Search)Replica

This adds partial, testing-focused support for SQLite, as well as removing
some translated log messages that required initializing i18n just for
testing.

* avoid returning master twice when no replicas are configured

* remove duplicate indexes

* unit test GetAllConns

i18n/en.json

@@ -5802,10 +5802,6 @@
     "id": "store.sql.create_column_missing_driver.critical",
     "translation": "Failed to create column because of missing driver"
   },
-  {
-    "id": "store.sql.create_index.critical",
-    "translation": "Failed to create index %v"
-  },
   {
     "id": "store.sql.create_index_missing_driver.critical",
     "translation": "Failed to create index because of missing driver"
@@ -5830,10 +5826,6 @@
     "id": "store.sql.maxlength_column.critical",
     "translation": "Failed to get max length of column %v"
   },
-  {
-    "id": "store.sql.open_conn.critical",
-    "translation": "Failed to open SQL connection to err:%v"
-  },
   {
     "id": "store.sql.open_conn.panic",
     "translation": "Failed to open SQL connection %v"
@@ -5854,10 +5846,6 @@
     "id": "store.sql.schema_out_of_date.warn",
     "translation": "The database schema version of %v appears to be out of date"
   },
-  {
-    "id": "store.sql.schema_set.info",
-    "translation": "The database schema has been set to version %v"
-  },
   {
     "id": "store.sql.schema_upgrade_attempt.warn",
     "translation": "Attempting to upgrade the database schema version to %v"
@@ -6590,10 +6578,6 @@
     "id": "store.sql_preference.delete.app_error",
     "translation": "We encountered an error while deleting preferences"
   },
-  {
-    "id": "store.sql_preference.delete_unused_features.debug",
-    "translation": "Deleting any unused pre-release features"
-  },
   {
     "id": "store.sql_preference.get.app_error",
     "translation": "We encountered an error while finding preferences"