[DDW-436] Fix leftovers not being displayed correctly

[thedanheller]

This PR fixes leftovers not being displayed correctly.

Todos

• Remove hardcoded leftovers value
• Subtract leftovers from the total amount

Screenshots

The issues

1. The leftovers value is shown, even though in the result the source wallet (TestB) is left with 0 ADA;
2. The leftovers value is not subtracted from the total amount.

Issues fixed

1. The leftovers value is not shown when not provided by the API:

2. When leftovers value is present, it is subtracted from the total amount:

---

Testing Checklist

• Slack QA thread
• Make a normal transferring funds operation. The leftovers will probably not appear, as it is a very rare case.
• On Storybook, change the leftovers slider. Then the value is zero, the leftovers should not appear on the screen. Other values should alter the Total amount.

---

Review Checklist

Basics

• PR has been assigned and has appropriate labels (feature/bug/chore, release-x.x.x)
• PR is updated to the most recent version of the target branch (and there are no conflicts)
• PR has a good description that summarizes all changes
• PR has default-sized Daedalus window screenshots or animated GIFs of important UI changes:
  • In English
  • In Japanese
• CHANGELOG entry has been added to the top of the appropriate section (Features, Fixes, Chores) and is linked to the correct PR on GitHub
• Automated tests: All acceptance and unit tests are passing (yarn test)
• Manual tests (minimum tests should cover newly added feature/fix): App works correctly in development build (yarn dev)
• Manual tests (minimum tests should cover newly added feature/fix): App works correctly in production build (yarn package / CI builds)
• There are no flow errors or warnings (yarn flow:test)
• There are no lint errors or warnings (yarn lint)
• There are no prettier errors or warnings (yarn prettier:check)
• There are no missing translations (running yarn manage:translations produces no changes)
• Text changes are proofread and approved (Jane Wild / Amy Reeve)
• Japanese text changes are proofread and approved (Junko Oda)
• UI changes look good in all themes (Alexander Rukin)
• Storybook works and no stories are broken (yarn storybook)
• In case of dependency changes yarn.lock file is updated

Code Quality

• Important parts of the code are properly commented and documented
• Code is properly typed with flow
• React components are split-up enough to avoid unnecessary re-renderings
• Any code that only works in main process is neatly separated from components

Testing

• New feature/change is covered by acceptance tests
• New feature/change is manually tested and approved by QA team
• All existing acceptance tests are still up-to-date
• New feature/change is covered by Daedalus Testing scenario
• All existing Daedalus Testing scenarios are still up-to-date

After Review

• Merge the PR
• Delete the source branch
• Move the ticket to done column on the YouTrack board
• Update Slack QA thread by marking it with a green checkmark

[nikolaglumac]

Nice fix @daniloprates 💯