vpp: T7972: Improve nat44 no-forwarding feature name and description in CLI

[natali-rs1985]

New CLI command for nat44 no-forwarding:

vyos@vyos# set vpp settings nat44 processing-mode
Possible completions:
   static-dynamic       Process traffic by both static rules and dynamic NAT (default)
   static-bypass        Process traffic by static NAT rules only, pass without NAT if not matched

Change summary

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Code style update (formatting, renaming)
• Refactoring (no functional changes)
• Migration from an old Vyatta component to vyos-1x, please link to related PR inside obsoleted component
• Other (please describe):

Related Task(s)

• https://vyos.dev/T7972

Related PR(s)

vyos/vyos-documentation#1717

How to test / Smoketest result

vyos@vyos# /usr/libexec/vyos/tests/smoke/cli/test_vpp.py -k test_16_vpp_nat
test_16_vpp_nat (__main__.TestVPP.test_16_vpp_nat) ... ok

----------------------------------------------------------------------
Ran 1 test in 56.907s

OK

Checklist:

• I have read the CONTRIBUTING document
• I have linked this PR to one or more Phabricator Task(s)
• I have run the components SMOKETESTS if applicable
• My commit headlines contain a valid Task id
• My change requires a change to the documentation
• I have updated the documentation accordingly

[github-actions]

👍
No issues in PR Title / Commit Title

[natali-rs1985]

@sever-sever All change requests were addressed

[github-actions]

CI integration 👍 passed!

Details

CI logs

• CLI Smoketests (no interfaces) 👍 passed
• CLI Smoketests VPP 👍 passed
• CLI Smoketests (interfaces only) 👍 passed
• Config tests 👍 passed
• Config tests VPP 👍 passed
• RAID1 tests 👍 passed
• TPM tests 👍 passed

[sever-sever]

All my requests have been fulfilled.
Migrate NAT no-forwarding option to more clear CLI syntax/meaning

[zdc]

Shouldn't the static-bypass option to be the default one?

How I read this.

• Before: by default, nat44 forwarding was enabled (no no-forwarding in CLI).
• After: by default, nat44 forwarding is disabled, because static-dynamic is a default value and enable_forwarding = config['processing_mode'] == 'static-bypass'

Am I missing something?