Replace go-migrate with morph (#19116)

db/migrations/postgres/000031_create_remote_clusters.up.sql

@@ -0,0 +1,16 @@
+CREATE TABLE IF NOT EXISTS remoteclusters (
+    remoteid VARCHAR(26) NOT NULL,
+    remoteteamid VARCHAR(26),
+    name VARCHAR(64) NOT NULL,
+    displayname VARCHAR(64),
+    siteurl VARCHAR(512),
+    createat bigint,
+    lastpingat bigint,
+    token VARCHAR(26),
+    remotetoken VARCHAR(26),
+    topics VARCHAR(512),
+    creatorid VARCHAR(26),
+    PRIMARY KEY (remoteid, name)
+);
+
+CREATE UNIQUE INDEX IF NOT EXISTS remote_clusters_site_url_unique ON remoteclusters (siteurl, remoteteamid);