Add user agent from Webview property as default in HTTP interceptor (Android)

[Fatxx]

Description

The userAgent property provided in the Webview component on Android isn't being properly set in the interceptor, now it should use the provided property value and fallback to the device user agent when this property is not defined.

Screenshots/Recordings

With userAgent property defined in WebView:

Without userAgent property in WebView:

Related slack thread: https://consensys.slack.com/archives/CBW7S9FSN/p1659995161910989

Issue

Progresses #4829

Checklist

• [ ] There is a related GitHub issue
• [ ] Tests are included if applicable
• [ ] Any added code is fully documented

[github-actions[bot]]

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[wachunei]

This is working as expected for the on-ramp requirements 👍