feat(toolbar-search): add filteredRowIds prop to support pagination

[metonym]

Closes #1393

Currently, the built-in filter behavior for DataTable does not support pagination. For example, filtering a table will not update the total items displayed in the Pagination component.

This can be solved by exposing the filtered row ids in ToolbarSearch through a filteredRowIds prop. The value of this prop can be bound to and passed to Pagination and is generally useful.

Sample Usage

<script>
  import {
    DataTable,
    Toolbar,
    ToolbarContent,
    ToolbarSearch,
    Pagination,
  } from "carbon-components-svelte";

  let rows = Array.from({ length: 10 }).map((_, i) => ({
    id: i,
    name: "Load Balancer " + (i + 1),
    protocol: "HTTP",
    port: 3000 + i * 10,
    rule: i % 2 ? "Round robin" : "DNS delegation",
  }));
  let pageSize = 5;
  let page = 1;
  let filteredRowIds = [];

  $: console.log("filteredRowIds", filteredRowIds);
</script>

<DataTable
  headers="{[
    { key: 'name', value: 'Name' },
    { key: 'protocol', value: 'Protocol' },
    { key: 'port', value: 'Port' },
    { key: 'rule', value: 'Rule' },
  ]}"
  rows="{rows}"
  pageSize="{pageSize}"
  page="{page}"
>
  <Toolbar>
    <ToolbarContent>
      <ToolbarSearch
        persistent
        value="round"
        shouldFilterRows
        bind:filteredRowIds
      />
    </ToolbarContent>
  </Toolbar>
</DataTable>

<Pagination
  bind:pageSize
  bind:page
  totalItems="{filteredRowIds.length}"
  pageSizeInputDisabled
/>

This PR updates and simplifies the filterable DataTable examples.