Include Webhook ClientState in Model

[singingknight]

Webhook ClientState has been part of the Provisioning Schema since 2019-09, but not included in the Models

This Pull Request will cause the ClientState in a PnP Template like this to be applied and not just ignored:

<?xml version="1.0" encoding="utf-8"?>
<pnp:Provisioning xmlns:pnp="http://schemas.dev.office.com/PnP/2022/09/ProvisioningSchema">
  <pnp:Preferences Generator="Human being" />
  <pnp:Templates ID="CONTAINER-TEMPLATE">
    <pnp:ProvisioningTemplate ID="TEMPLATE" Version="1" BaseSiteTemplate="SITEPAGEPUBLISHING#0" Scope="RootSite">
      <pnp:Lists>
        <pnp:ListInstance ...>
          <pnp:Webhooks>
            <pnp:Webhook ServerNotificationUrl="https://..." ExpiresInDays="90" ClientState="my-important-info" />
          </pnp:Webhooks>
        </pnp:ListInstance>
      </pnp:Lists>
    </pnp:ProvisioningTemplate>
  </pnp:Templates>
</pnp:Provisioning>