[Bug] Expand fails to recognize user-defined tablespaces

### Apache Cloudberry version

2.1.0-incubating

### What happened

When user-defined tablespaces exist in the cluster, gpexpand does not create the `newTableSpaceInfo.json` file in the new segment template when running with a config file (non-interactive mode).

This leads to broken symlinks for tablespaces and causes failures during the prepare_schema() stage.

The problem is present in two methods within the same file:
1. `read_tablespace_file()` in `gpMgmt/bin/gpexpand` (lines 1219–1285)
2. `generate_tablespace_inputfile()` in `gpMgmt/bin/gpexpand` (lines 1114–1148)

- `read_tablespace_file()` (line 1244):
```python
tblspc_oids = os.listdir(coordinator_tblspc_dir)
tblspc_oid_names = self.get_tablespace_oid_names()
flag = False
for oid in tblspc_oids:
if oid in tblspc_oid_names: <---
flag = True
if not flag:
return None
```

- `generate_tablespace_inputfile()` (line 1124)
```python
tblspc_oid_names = self.get_tablespace_oid_names()
tblspc_info = {}

for oid in tblspc_oids:
if oid not in tblspc_oid_names: <---
continue
location = os.path.dirname(os.readlink(os.path.join(coordinator_tblspc_dir,
oid)))
tblspc_info[oid] = {"location": location,
"name": tblspc_oid_names[int(oid)]}
```

Root cause: type mismatch between string values returned by `os.listdir()` and integer keys returned by the SQL query `SELECT oid, spcname FROM pg_tablespace`.

When attaching to the process and debugging, the types differ, causing this issue:

- type mismatch

- `newTableSpaceInfo `is `None`

Impact:
- `newTableSpaceInfo `is always None.
- `_handle_tablespace_template()` is never invoked.
- `newTableSpaceInfo.json` is not included in the template tar.
- `gpconfigurenewsegment `on new hosts does not fix tablespace symlinks.
- new segments start with broken symlinks.

### What you think should happen instead

To fix the issue, unify the data types in both methods:
- In `generate_tablespace_inputfile()`:
```python
for oid in tblspc_oids:
if int(oid) not in tblspc_oid_names:
```

- In `read_tablespace_file()`:
```python
tblspc_oids = os.listdir(coordinator_tblspc_dir)
tblspc_oid_names = self.get_tablespace_oid_names()
flag = False
for oid in tblspc_oids:
if int(oid) in tblspc_oid_names:
```

After this change, `newTableSpaceInfo `is no longer `None`:

### How to reproduce

1. Connect to the database:
```sh
gpadmin@cbdb-mdw:~$ psql warehouse
```

2. Create a user-defined tablespace:
```sql
warehouse=# CREATE TABLESPACE ts_stage_logs LOCATION '/tblspc_stage_logs';
```

```
warehouse=# SELECT * FROM pg_tablespace;
oid | spcname | spcowner | spcacl | spcoptions | spcfilehandlersrc | spcfilehandlerbin
-------+---------------+----------+--------+------------+-------------------+-------------------
1663 | pg_default | 10 | | | |
1664 | pg_global | 10 | | | |
17019 | ts_stage_logs | 10 | | | |
(3 rows)
```

3. Create an append-optimized columnar table and populate it with test data:
```sql
warehouse=# CREATE TABLE logs_aot (
id BIGSERIAL,
log_timestamp TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
log_level VARCHAR(10)
)
WITH (
APPENDONLY = TRUE,
ORIENTATION = COLUMN
)
TABLESPACE ts_stage_logs
DISTRIBUTED BY (id);

warehouse=# INSERT INTO logs_aot (
log_timestamp,
log_level
)
SELECT
NOW() - (random() * INTERVAL '90 days'),
(ARRAY['INFO', 'WARN', 'ERROR', 'DEBUG'])[floor(random() * 4 + 1)]
FROM generate_series(1, 8000);
```

4. Prepare the expansion configuration file for adding 2 new hosts to the cluster:
```
sdw3-new|sdw3-new|6000|/primary_data/gpseg4|10|4|p
sdw4-new|sdw4-new|7000|/mirror_data/gpseg4|11|4|m
sdw3-new|sdw3-new|6001|/primary_data/gpseg5|12|5|p
sdw4-new|sdw4-new|7001|/mirror_data/gpseg5|13|5|m
sdw4-new|sdw4-new|6000|/primary_data/gpseg6|14|6|p
sdw3-new|sdw3-new|7000|/mirror_data/gpseg6|15|6|m
sdw4-new|sdw4-new|6001|/primary_data/gpseg7|16|7|p
sdw3-new|sdw3-new|7001|/mirror_data/gpseg7|17|7|m
```

5. Start the expansion process (non-interactive mode):
```sh
gpadmin@cbdb-mdw:~$ gpexpand -i expand.cfg
```

6. The following error appears in the logs (log truncated for readability.)
```
20260805:18:33:04:052024 gpexpand:cbdb-mdw:gpadmin-[INFO]:-Heap checksum setting consistent across cluster
20260805:18:33:04:052024 gpexpand:cbdb-mdw:gpadmin-[INFO]:-Syncing Apache Cloudberry extensions
20260805:18:33:04:052024 gpexpand:cbdb-mdw:gpadmin-[INFO]:-Locking catalog
20260805:18:33:05:052024 gpexpand:cbdb-mdw:gpadmin-[INFO]:-Locked catalog
20260805:18:33:06:052024 gpexpand:cbdb-mdw:gpadmin-[INFO]:-Creating segment template
20260805:18:33:07:052024 gpexpand:cbdb-mdw:gpadmin-[INFO]:-Copying postgresql.conf from existing segment into template
20260805:18:33:08:052024 gpexpand:cbdb-mdw:gpadmin-[INFO]:-Copying pg_hba.conf from existing segment into template
20260805:18:33:09:052024 gpexpand:cbdb-mdw:gpadmin-[INFO]:-Creating schema tar file
...
20260805:18:33:26:052024 gpexpand:cbdb-mdw:gpadmin-[INFO]:-Populating gpexpand.status_detail with data from database postgres
20260805:18:33:27:052024 gpexpand:cbdb-mdw:gpadmin-[INFO]:-Populating gpexpand.status_detail with data from database warehouse
20260805:18:33:27:052024 gpexpand:cbdb-mdw:gpadmin-[ERROR]:-gpexpand failed: ERROR: could not open file "pg_tblspc/17019/GPDB_3_302606111/17018/16386": No such file or directory (seg6 203.0.113.5:6000 pid=21449)

Exiting...
20260805:18:33:27:052024 gpexpand:cbdb-mdw:gpadmin-[ERROR]:-gpexpand is past the point of rollback. Any remaining issues must be addressed outside of gpexpand.
20260805:18:33:27:052024 gpexpand:cbdb-mdw:gpadmin-[INFO]:-Shutting down gpexpand...
```

Hope this analysis is helpful.

### Operating System

Ubuntu 22.04

### Anything else

_No response_

### Are you willing to submit PR?

- [ ] Yes, I am willing to submit a PR!

### Code of Conduct

- [x] I agree to follow this project's [Code of Conduct](https://github.com/apache/cloudberry/blob/main/CODE_OF_CONDUCT.md).

Start in gpMgmt/bin/gpexpand by reading read_tablespace_file() and generate_tablespace_inputfile(), focusing on how os.listdir() values are compared with get_tablespace_oid_names() results. Run the provided user-defined tablespace and non-interactive gpexpand reproduction, then verify that newTableSpaceInfo.json is generated and tablespace symlinks are fixed on new segments.

Written by the indexing model from the issue text.