add: check port, get free port is un available

[singjc]

Description

Add method to check if port is free, if not get a free port.

Type of change

Please delete options that are not relevant.

• [x] New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Tested running GUI from CLI

Test Configuration:

• Firmware version: popOS
• Hardware: system76

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [x] Any dependent changes have been merged and published in downstream modules

  Contents (#133)

Other

• check port, get free port is un available