Replace v1 base with restfly

[SteveMcGrath]

Description

Addresses depreciation of pyTenable's v1 connection library and transitions that connection logic to the RESTfly library instead.

Type of change

Please delete options that are not relevant.

• 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 not work as expected)
  1. This could break existing code that leverages specific Exception handling.
• This change requires a documentation update
  1. Documentation would need to be updated around exception handling.

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Local testing with py.test
• Local testing against python matrix using act.

Test Configuration:

• Python Version(s) Tested: 3.6, 3.7, 3.8, 3.9
• Tenable.sc version (if necessary): 3.18

Checklist:

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

[nkeuning]

Everything looks good to me