feat: add chat-input

[Killusions]

Add the chat-input component, needed for #600, uses #877 (merged)

Automatically expands based on text input (as per UX specs).

The actions and the disclaimer can also be provided in a declarative way.

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[Killusions]

@kfenner Should be ready now (but merge after the base chat messages because of the attachment list), the actions and the disclaimer can also be provided in a declarative way, automatically expands based on text input (as per UX specs), the default legal AI disclaimer will be defaulted in the (ai) chat container, as this input is not AI specific

[github-actions]

Documentation.
Examples.
Playwright report.

Coverage Reports:

• element-ng
• element-translate-ng

[Killusions]

@spike-rabbit @timowolf Anyone of you time to give it a review here? The actions and the disclaimer can be provided both in a model driven (should be used in most cases to follow UX guidelines) and in a declarative way (extensibility for custom actions like model selectors and custom disclaimer displaying)

[timowolf]

Fantastic.

[github-actions]

[siemens-element-bot]

🎉 This PR is included in version 48.3.0 🎉

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