Fix for flaky base node tests

[sdbondi]

Description

Base node and mempool integration tests construct their test networks using the most
optimal ordering. This reduces/removes test flakiness.

The databases files for nodes are no longer shared as this would cause
tests to sporadically fail on MacOS.

Motivation and Context

Improve test reliability

How Has This Been Tested?

N/A

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Feature refactor (No new feature or functional changes, but performance or technical debt improvements)
• New Tests
• Documentation

Checklist:

• I'm merging against the development branch.
• I ran cargo-fmt --all before pushing.
• I have squashed my commits into a single commit.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.

[philipr-za]

LGTM