feat(Datagrid): add ai slug support to col headers

[matthewgallo]

Contributes to #4162

Adds support for the AI slug to be placed within column headers, I included a new story within the Datagrid to demonstrate this as well.

What did you change?

packages/core/story-structure.js
packages/ibm-products-styles/src/components/Datagrid/styles/_datagrid.scss
packages/ibm-products/src/components/Datagrid/Datagrid.stories.js
packages/ibm-products/src/components/Datagrid/Datagrid/DatagridHeaderRow.js
packages/ibm-products/src/components/Datagrid/Datagrid/addons/Slug/ColumnHeaderSlug.js
packages/ibm-products/src/components/Datagrid/Extensions/Slug/Slug.stories.js
packages/ibm-products/src/components/Datagrid/useDefaultStringRenderer.js
packages/ibm-products/src/components/Datagrid/useSortableColumns.js

How did you test and verify your work?

Storybook

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