Auto tapper sometimes taps extra lands for no reason

**Describe the bug**
Playing a spell and pressing "auto" instead of tapping manually sometimes results in it tapping too many lands and floating mana.

**To Reproduce**
I don't know how exactly to reproduce it, but it often happens when you have a land that taps for more than one mana.

**Expected behavior**
It should tap only the lands needed to pay for the spell.

**Screenshots**

Here in the screenshot I cast Witherbloom, costing 5 mana with the affinity discount. I had 6 mana worth of untapped lands, since the Ancient Tomb taps for 2. It tapped all of them and floated a colorless, when it could have left the Svogthos or a forest untapped and still paid for the spell.

**Desktop (please complete the following information):**
- OS: Linux
- Version: 2.0.15 snapshot 08.25

**Additional context**
PLEASE make it show a preview of how it's gonna auto tap, like Arena does. Then at least I could catch the mistake and tap manually instead..

Start by reproducing the auto-tapping behavior with a spell and a land that produces more than one mana, such as Ancient Tomb, using the issue's screenshot and described state. Trace the auto-tap entry point and verify that only the mana required for the spell is tapped, without leaving floating mana; no source file or test is named in the issue.

Written by the indexing model from the issue text.