### What

Add support for environment variables in permission filters by
introducing a new `ValueFromEnv` variant. This enhancement allows users
to reference environment variables in permission rules and value
expressions, similar to how `sessionVariable` and `literal` values work.

Key changes:
- Added `ValueFromEnv` variant to `ValueExpression` and
`ValueExpressionOrPredicate`
- Updated environment variables handling to support JSON values instead
of strings (we need this as the literal values can be something other
than `String` as well
- Added changes to JSON schemas for the types as well

### How

1. Modified `crates/open-dds/src/permissions.rs`:
- Split `ValueExpression` and `ValueExpressionOrPredicate` into base
enums and their schema implementation counterparts
(`ValueExpressionImpl` and `ValueExpressionOrPredicateImpl`)
- Added `ValueFromEnv` variant to support environment variable
references
   - Implemented proper JSON schema generation through `OpenDd` trait

2. Updated environment variables handling in
`build/environment_variables.rs`:
- Changed value type from `String` to `serde_json::Value` to support
various value types
   - Updated injection and restoration logic to handle JSON values

Users can now reference environment variables in their permissions
metadata:
```json
{
  "role": "artist1",
  "select": {
    "filter": {
      "fieldComparison": {
        "field": "ArtistId",
        "operator": "_eq",
        "value": {
          "valueFromEnv": "ENV_VAR1"
        }
      }
    }
  }
}
```

### Internal details

V3_GIT_ORIGIN_REV_ID: 2dc2da8b7266d9c68887ac27990ba8bbea17166b