R1:76af4d649bfc

Fix ContainsConstraints for array-valued custom field constraints in "*.search" methods

Summary: Fixes T11593. We ask for a list of values when searching for custom "link" fields, but don't handle it correctly when actually construcitng a query.

Test Plan:
Added this custom field:

```
{
"mycompany.target-version": {
"name": "Target Version",
"type": "link",
"search": true
}
}
```

Set a task to "beta". Let daemons index it. Queried for:

```
constraints: {
"custom.mycompany.target…