Fix: corrected submodule arguments and added output for private IP of firewall

[ASHR4]

Description

• Added firewalls private IPs to the outputs. Fixes [AVM Module Issue]: Cannot output firewall private or public ip addresses #106
• Pass through zones attribute to submodule and amend submodule to set attribute. Previously you could configure this attribute but it wasn't set at the resource level. Closes [AVM Module Issue]: Firewall zones value not being passed to submodule and submodule resources #145
• Corrected the s2s vpn gateway scale unit argument being passed to submodule incorrectly/. Closes [AVM Module Issue]: S2S VPN Gateway scale units value not being passed thru the sub-module #143

Type of Change

• Non-module change (e.g. CI/CD, documentation, etc.)
• Azure Verified Module updates:
  • Bugfix containing backwards compatible bug fixes
    • Someone has opened a bug report issue, and I have included "Closes #{bug_report_issue_number}" in the PR description.
    • The bug was found by the module author, and no one has opened an issue to report it yet.
  • Feature update backwards compatible feature updates.
  • Breaking changes.
  • Update to documentation

Checklist

• I'm sure there are no other open Pull Requests for the same update/change
• My corresponding pipelines / checks run clean and green without any errors or warnings
• I did run all pre-commit checks