[support a REST API] Update Extensions Site Settings for new Trusted Extensions options

[jacksonlauren]

Allow users to set the new Trusted Extensions settings

GET /api/api-version/sites/site-luid/settings/extensions
SET /api/api-version/sites/site-luid/settings/extensions

{
    "extensionsEnabled": "true",
    "allowTrusted": "false",
    "includeSandboxed": "false",
    "includeTableauBuilt": "false",
    "includePartnerBuilt": "false",
    "safeList": {
        ...
    }
}