Forward autocomplete in nimble-text-field

[kevtan-ni]

Pull Request

🤨 Rationale

Partially addresses #2914

nimble-text-field's real lives in shadow DOM. Browsers read that input's autocomplete attribute to autofill login fields, but nimble-text-field was not forwarding this attribute so username/password fields weren't being recognized.

👩‍💻 Implementation

• Add a public autocomplete attribute and forward it to the internal input

🧪 Testing

• Added unit tests to verifying autocomplete is forwarded to the internal input when set and absent when unset

✅ Checklist

• I have updated the project documentation to reflect my changes or determined no changes are needed.