Transfer by dialpad: Spacing-related fixes

[anoadragon453]

This PR builds on top of #6217.

It aims to cover:

• Increasing the size of the dial pad in general.
• Spacing the number buttons out a bit more from each other.
• Shrinking the separator bar between the text entry field and number buttons.

The standalone dial pad looks like:

The in-call dial pad looks like:

And the transfer dial pad looks like:

Future PRs will:

• put letters under each num button (and darken the font).
• move the backspace from a distinct button to the right side of the field.