[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": {
        ...
    }
}

[bcantoni]

This request is specifically about the new Trusted Extensions, but in general TSC doesn't have any of the Site Settings for Extensions yet.

REST API reference: https://help.tableau.com/current/api/rest_api/en-us/REST/rest_api_ref_tableau_extensions_settings.htm