Enable early exiting if BackgroundDevnet fails

[FabijanC]

Usage related changes

Hopefully none.

Development related changes

• Change order of actions in main:
  • Perform port binding after creating Starknet and Api objects (Starknet creation might fail).
• If BackgroundDevnet fails, early exiting is enabled in port search to prevent unnecessary waiting for 30 seconds.

Checklist:

• Checked out the contribution guidelines
• Applied formatting - ./scripts/format.sh
• No linter errors - ./scripts/clippy_check.sh
• No unused dependencies - ./scripts/check_unused_deps.sh
• No spelling errors - ./scripts/check_spelling.sh
• Performed code self-review
• Rebased to the latest commit of the target branch (or merged it into my branch)
  • Once you make the PR reviewable, please avoid force-pushing
• Updated the docs if needed - ./website/README.md
• Linked the issues resolvable by this PR - linking info
• Updated the tests if needed; all passing - execution info
  • All tests passing except those blocked by Failing tests requiring USC that supports Sierra 1.7.0 #680.