feat: add src_id and dst_id indexes to tailnet_tunnels (#12911)

Fixes #12780

Adds indexes to the `tailnet_tunnels` table to speed up `GetTailnetTunnelPeerIDs` and `GetTailnetTunnelPeerBindings` queries, which match on `src_id` and `dst_id`.

coderd/database/migrations/000206_add_tailnet_tunnels_indexes.down.sql

@@ -0,0 +1,2 @@
+DROP INDEX idx_tailnet_tunnels_src_id;
+DROP INDEX idx_tailnet_tunnels_dst_id;

coderd/database/migrations/000206_add_tailnet_tunnels_indexes.up.sql

@@ -0,0 +1,3 @@
+-- Since src_id and dst_id are UUIDs, we only ever compare them with equality, so hash is better
+CREATE INDEX idx_tailnet_tunnels_src_id ON tailnet_tunnels USING hash (src_id);
+CREATE INDEX idx_tailnet_tunnels_dst_id ON tailnet_tunnels USING hash (dst_id);