opt: redundant locality-optimized search operator when only targeting remote regions

Set up MR cluster via demo
```
cockroach demo movr --global --nodes 9 --multitenant=false --insecure
```
and then
```sql
ALTER DATABASE movr PRIMARY REGION "us-east1";
ALTER DATABASE movr ADD REGION "europe-west1";
ALTER DATABASE movr ADD REGION "us-west1";

CREATE TABLE parent (
p_id INT PRIMARY KEY,
p_attr INT
) LOCALITY REGIONAL BY ROW;

CREATE TABLE child (
c_id INT PRIMARY KEY,
c_p_id INT REFERENCES parent (p_id)
) LOCALITY REGIONAL BY ROW;
```
The query targeting only remote regions has redundant locality-optimized search operator:
```sql
EXPLAIN (opt) SELECT * FROM child INNER LOOKUP JOIN parent ON c_p_id = p_id AND child.crdb_region IN ('us-west1', 'europe-west1') LIMIT 3;
```
```
project
└── limit
├── project
│ └── locality-optimized-search
│ ├── values
│ └── inner-join (lookup parent)
│ ├── flags: force lookup join (into right side)
│ ├── lookup columns are key
│ ├── scan child
│ │ └── constraint: /19/17
│ │ ├── [/'europe-west1' - /'europe-west1']
│ │ └── [/'us-west1' - /'us-west1']
│ └── filters (true)
└── 3
```
```
• limit
│ count: 3
│
└── • union all
│
├── • norows
│
└── • lookup join
│ table: parent@parent_pkey
│ equality cols are key
│ lookup condition: (crdb_region IN ('europe-west1', 'us-east1', 'us-west1')) AND (c_p_id = p_id)
│
└── • scan
missing stats
table: child@child_pkey
spans: [/'europe-west1' - /'europe-west1'] [/'us-west1' - /'us-west1']
```
Not a big deal, but it'd be great if we could remove this redundant `locality-optimized-search` operator.

Jira issue: CRDB-26705