go: sqle/dsess: session.go: Fix transaction savepoint creation when cluster replication is enabled.

Cluster replication creates a system database, `dolt_cluster`, which does not
support transactions. There are also UserSpaceDatabases which do not support
CreateTransaction. CreateTransaction has special code to avoid visiting them
when recording the start transaction state. CreateSavepoint needed to be
updated with that logic as well.

integration-tests/go-sql-server-driver/tests/sql-server-cluster.yaml

@@ -1426,6 +1426,76 @@ tests:
     queries:
     - exec: 'use repo1'
     - exec: 'call dolt_checkout("new_branch_name")'
+# At one point the dolt_cluster database interacted poorly with creating savepoints.
+- name: savepoints work on cluster replicated databases
+  multi_repos:
+  - name: server1
+    with_files:
+    - name: server.yaml
+      contents: |
+        log_level: trace
+        listener:
+          host: 0.0.0.0
+          port: 3309
+        cluster:
+          standby_remotes:
+          - name: standby
+            remote_url_template: http://localhost:3852/{database}
+          bootstrap_role: primary
+          bootstrap_epoch: 1
+          remotesapi:
+            port: 3851
+    server:
+      args: ["--config", "server.yaml"]
+      port: 3309
+  - name: server2
+    with_files:
+    - name: server.yaml
+      contents: |
+        log_level: trace
+        listener:
+          host: 0.0.0.0
+          port: 3310
+        cluster:
+          standby_remotes:
+          - name: standby
+            remote_url_template: http://localhost:3851/{database}
+          bootstrap_role: standby
+          bootstrap_epoch: 1
+          remotesapi:
+            port: 3852
+    server:
+      args: ["--config", "server.yaml"]
+      port: 3310
+  connections:
+  - on: server1
+    queries:
+    - exec: 'create database repo1'
+    - exec: 'use repo1'
+    - exec: 'create table vals (id int primary key, val int)'
+    - exec: 'begin'
+    - exec: 'savepoint before_values_inserted'
+    - exec: 'insert into vals values (1,1)'
+    - exec: 'insert into vals values (2,2)'
+    - exec: 'insert into vals values (3,3)'
+    - exec: 'insert into vals values (4,4)'
+    - exec: 'rollback to savepoint before_values_inserted'
+    - exec: 'commit'
+  - on: server1
+    queries:
+    - query: "select `database`, standby_remote, role, epoch, replication_lag_millis, current_error from dolt_cluster.dolt_cluster_status order by `database` asc"
+      result:
+        columns: ["database","standby_remote","role","epoch","replication_lag_millis","current_error"]
+        rows:
+        - ["repo1","standby","primary","1","0","NULL"]
+      retry_attempts: 100
+  - on: server2
+    queries:
+    - exec: 'use repo1'
+    - query: "select * from vals order by id asc"
+      result:
+        columns: ["id","val"]
+        rows: []
 - name: call dolt gc
   multi_repos:
   - name: server1
@@ -1956,4 +2026,4 @@ tests:
   connections:
     - on: server1
       queries:
-        - exec: "set foreign_key_checks=0"
+        - exec: "set foreign_key_checks=0"