David Martos 197cd4d665
Update margin between label and icon in Tab to better reflect Material specs (#140698)
This PR improves the distance between the label and the icon in the Tab widget. 
I updated the margin to 2 pixels, taken from the Figma design page for Material 3. On Material 2 I left the default value of 10 pixels.

Related to #128696 (In particular, the distance between label and icon)

Here are some screenshots for comparison. I looked a bit into the other mentioned issue of the tab height not following the M3 spec. Flutter uses 72 and the spec uses 64. But because Tab is a PreferredSizeWidget, I don't think there is an easy way to provide a different size depending on `ThemeData.useMaterial3`, because there is no `BuildContext` available.
I provide a sample image for the 64 height as well for context on the linked issue, even though it's not part of the PR changes.

The screenshots are taken side by side with the image at: https://m3.material.io/components/tabs/guidelines

## Original

![original](https://github.com/flutter/flutter/assets/22084723/f52d46bb-eaf9-4519-976e-9ea07c021e14)

## New (tab height = 72, Flutter default for 8 years)

![new_72](https://github.com/flutter/flutter/assets/22084723/8c9d3510-eaca-4b7d-92d8-0d06a7e75136)

## New (tab height = 64, M3 spec)

![new_64](https://github.com/flutter/flutter/assets/22084723/f8811b70-766f-4a4f-b069-33673b1e3744)
2024-01-18 23:04:26 +00:00
..
2024-01-18 18:38:00 +01:00

Flutter

Flutter is a new way to build high-performance, cross-platform mobile, web, and desktop apps. Flutter is optimized for today's — and tomorrow's — mobile and desktop devices. We are focused on low-latency input and high frame rates on all platforms.

See the getting started guide for information about using Flutter.