Update packages object (#1637)

## Summary

Updates the schema to better reflect the packages object -- packages can
be either:

* A list of Strings
* An object, where each key contains either a version string or an
object

## How was it tested?

Used the following package list: 

```json
  "packages": {
    "go":                          "latest",
    "runx:golangci/golangci-lint": "latest",
    "runx:mvdan/gofumpt":          "latest",
    "glibcLocales": {
      "version":            "latest",
      "excluded_platforms": ["aarch64-darwin"]
    }
  },
```

Author: Lagoja

.schema/devbox.schema.json

@@ -19,32 +19,45 @@
                         "type": "string"
                     }
                 },
-                {
-                    "type": "object",
-                    "description": "Name of each package in {\"name\": \"version\"} format.",
-                    "patternProperties": {
-                        ".*": {
-                            "type": "string",
-                            "description": "Version of the package to install."
-                        }
-                    }
-                },
                 {
                     "type": "object",
                     "description": "Name of each package in {\"name\": {\"version\": \"1.2.3\"}} format.",
                     "patternProperties": {
                         ".*": {
+                            "oneOf": [
+                            {
                             "type": "object",
                             "description": "Version number of the specified package in {\"version\": \"1.2.3\"} format.",
                             "properties": {
                                 "version": {
                                     "type": "string",
                                     "description": "Version of the package"
                                 },
-                                "platform": {},
-                                "excluded_platform": {},
-                                "glibc_patch": {}
+                                "platforms": {
+                                    "type": "array",
+                                    "description": "Names of platforms to install the package on. This package will be skipped for any platforms not on this list",
+                                    "items": {
+                                        "enum": ["i686-linux", "aarch64-linux", "aarch64-darwin", "x86_64-darwin", "x86_64-linux", "armv7l-linux"]
+                                    }
+                                },
+                                "excluded_platforms": {
+                                    "type": "array",
+                                    "description": "Names of platforms to exclude the package on",
+                                    "items": {
+                                        "enum": ["i686-linux", "aarch64-linux", "aarch64-darwin", "x86_64-darwin", "x86_64-linux", "armv7l-linux"]
+                                    }
+                                },
+                                "glibc_patch": {
+                                    "type":"boolean",
+                                    "description": "Whether to patch glibc to the latest available version for this package"
+                                }
                             }
+                        },
+                        {
+                            "type": "string",
+                            "description": "Version of the package to install."
+                        }
+                    ]
                         }
                     }
                 }