tests: withdrawals test improvements

[knst]

Issue being fixed or feature implemented

Split from #6615

What was done?

How Has This Been Tested?

Functional test feature_asset_locks.py run significantly faster:

• 1m40s vs 2m+ on my localhost
• it creates only 5 quorums against 6+ (previous version can create much more than 6 if random quorum choice is not favor)
• disk usage is 177mb again 200mb+

Breaking Changes

Please describe any breaking changes your code introduces

Checklist:

Go over all the following points, and put an x in all the boxes that apply.

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated relevant unit/integration/functional/e2e tests
• I have made corresponding changes to the documentation
• I have assigned this pull request to a milestone (for repository code-owners and collaborators only)

[github-actions]

This pull request has conflicts, please rebase.