cli: copy-pasting multi-stmt snippet seems to be broken

Running on current master with
```
./cockroach demo movr --global --nodes 9 --multitenant=false --insecure
```
and then copy-pasting this whole snippet to convert the `movr` database into MR (courtesy of @michae2):

```sql
ALTER DATABASE movr PRIMARY REGION "us-east1";
ALTER DATABASE movr ADD REGION "europe-west1";
ALTER DATABASE movr ADD REGION "us-west1";

ALTER TABLE promo_codes SET LOCALITY GLOBAL;

ALTER TABLE rides ADD COLUMN region crdb_internal_region AS (
CASE WHEN city = 'amsterdam' THEN 'europe-west1'
WHEN city = 'paris' THEN 'europe-west1'
WHEN city = 'rome' THEN 'europe-west1'
WHEN city = 'new york' THEN 'us-east1'
WHEN city = 'boston' THEN 'us-east1'
WHEN city = 'washington dc' THEN 'us-east1'
WHEN city = 'san francisco' THEN 'us-west1'
WHEN city = 'seattle' THEN 'us-west1'
WHEN city = 'los angeles' THEN 'us-west1'
END
) STORED;
ALTER TABLE rides ALTER COLUMN region SET NOT NULL;
ALTER TABLE rides SET LOCALITY REGIONAL BY ROW AS "region";

ALTER TABLE user_promo_codes
ADD CONSTRAINT user_promo_codes_code_fk
FOREIGN KEY (code)
REFERENCES promo_codes (code)
ON UPDATE CASCADE;
ALTER TABLE user_promo_codes ADD COLUMN region crdb_internal_region AS (
CASE WHEN city = 'amsterdam' THEN 'europe-west1'
WHEN city = 'paris' THEN 'europe-west1'
WHEN city = 'rome' THEN 'europe-west1'
WHEN city = 'new york' THEN 'us-east1'
WHEN city = 'boston' THEN 'us-east1'
WHEN city = 'washington dc' THEN 'us-east1'
WHEN city = 'san francisco' THEN 'us-west1'
WHEN city = 'seattle' THEN 'us-west1'
WHEN city = 'los angeles' THEN 'us-west1'
END
) STORED;
ALTER TABLE user_promo_codes ALTER COLUMN region SET NOT NULL;
ALTER TABLE user_promo_codes SET LOCALITY REGIONAL BY ROW AS "region";

ALTER TABLE users ADD COLUMN region crdb_internal_region AS (
CASE WHEN city = 'amsterdam' THEN 'europe-west1'
WHEN city = 'paris' THEN 'europe-west1'
WHEN city = 'rome' THEN 'europe-west1'
WHEN city = 'new york' THEN 'us-east1'
WHEN city = 'boston' THEN 'us-east1'
WHEN city = 'washington dc' THEN 'us-east1'
WHEN city = 'san francisco' THEN 'us-west1'
WHEN city = 'seattle' THEN 'us-west1'
WHEN city = 'los angeles' THEN 'us-west1'
END
) STORED;
ALTER TABLE users ALTER COLUMN region SET NOT NULL;
ALTER TABLE users SET LOCALITY REGIONAL BY ROW AS "region";

ALTER TABLE vehicle_location_histories ADD COLUMN region crdb_internal_region AS (
CASE WHEN city = 'amsterdam' THEN 'europe-west1'
WHEN city = 'paris' THEN 'europe-west1'
WHEN city = 'rome' THEN 'europe-west1'
WHEN city = 'new york' THEN 'us-east1'
WHEN city = 'boston' THEN 'us-east1'
WHEN city = 'washington dc' THEN 'us-east1'
WHEN city = 'san francisco' THEN 'us-west1'
WHEN city = 'seattle' THEN 'us-west1'
WHEN city = 'los angeles' THEN 'us-west1'
END
) STORED;
ALTER TABLE vehicle_location_histories ALTER COLUMN region SET NOT NULL;
ALTER TABLE vehicle_location_histories SET LOCALITY REGIONAL BY ROW AS "region";

ALTER TABLE vehicles ADD COLUMN region crdb_internal_region AS (
CASE WHEN city = 'amsterdam' THEN 'europe-west1'
WHEN city = 'paris' THEN 'europe-west1'
WHEN city = 'rome' THEN 'europe-west1'
WHEN city = 'new york' THEN 'us-east1'
WHEN city = 'boston' THEN 'us-east1'
WHEN city = 'washington dc' THEN 'us-east1'
WHEN city = 'san francisco' THEN 'us-west1'
WHEN city = 'seattle' THEN 'us-west1'
WHEN city = 'los angeles' THEN 'us-west1'
END
) STORED;
ALTER TABLE vehicles ALTER COLUMN region SET NOT NULL;
ALTER TABLE vehicles SET LOCALITY REGIONAL BY ROW AS "region";

SELECT ' done';
```

seems to break the updated CLI.

First, I see this
```
...
WHEN city = 'san francisco' THEN 'us-west1'
WHEN city = 'seattle' THE WHEN city = 'seattle' THE WHEN city = 'seattle' THE WHEN city = 'seattle' THE WHEN city = 'seattle' THE WHEN city = 'seattle' THE WHEN city = 'seattle' THE WHEN city = 'seattle' THE WHEN city = 'seattle' THE WHEN city = 'seattle' THE WHEN city = 'seattle' THE WHEN city = 'seattle' THE WHEN city = 'seattle' THE WHEN city = 'seattle' THE WHEN city = 'seattle' THE WHEN city = 'seattle' THE WHEN city = 'sALTER DATABASE PRIMARY REGION

Time: 1.350s total (execution 1.340s / network 0.010s)
```
and then
```
root@127.0.0.1:26257/movr> NOT NULL;
invalid syntax: statement ignored: at or near "not": syntax error
SQLSTATE: 42601
DETAIL: source SQL:
NOT NULL
^
root@127.0.0.1:26257/movr> ty = 'rome' THEN 'europe-west1'
-> WHEN city = 'new york' THEN 'us-east1'
-> WHEN city = 'boston' THEN 'us-east1'
-> WHEN city = 'washington dc' THEN 'us-east1'
-> WHEN city = 'san francisco' THEN 'us-west1'
-> WHEN city = 'seattle' THE WHEN city = 'seattle' THE WHEN city = 'seattle' THE WHEN city = 'seattle' THE
-> WHEN city = 'seattle' THE WHEN city = 'seattle' THE WHEN city = 'seattle' THE WHEN city = 'seattle' THE
-> WHEN city = 'seattle' THE WHEN city = 'seattle' THE WHEN city = 'seattle' THE WHEN city = 'seattle' THE
-> WHEN city = 'seattle' THE WHEN city = 'seattle' THE WHEN city = 'seattle' THE WHEN city = 'seattle' THE
-> WHEN city = 'seattle' T WHEN city = 'washington dc' THEN 'us-east1'
-> WHEN city = 'san francisco' THEN 'us-west1'
-> WHEN city = 'seattle' THEN 'us-west1'
-> WHEN city = 'los angeles' THEN 'us-west1'
-> END
-> ) STORED;
invalid syntax: statement ignored: at or near "ty": syntax error
SQLSTATE: 42601
DETAIL: source SQL:
ty = 'rome' THEN 'europe-west1'
^
root@127.0.0.1:26257/movr> UMN region SET NOT NULL;
invalid syntax: statement ignored: at or near "umn": syntax error
SQLSTATE: 42601
DETAIL: source SQL:
UMN region SET NOT NULL
^
```
Doing the same on 22.2.6 works. cc @knz

Jira issue: CRDB-26676

Reproduce the failure by running the provided ./cockroach demo movr command and pasting the SQL snippet, then compare it with 22.2.6. Trace the CLI's multi-statement paste handling from that entry point; done means the complete snippet executes without duplicated or corrupted input.

Written by the indexing model from the issue text.