[fix] fixup json tags for VPCs + LinodeMachines

[rosskirkpat]

What this PR does / why we need it:

• fixes an issue with json tags (related to the changes made in [improvement] [breaking] make subnetID optional and align new interface field names with existing field names #880) when converting a v1alpha2 LinodeVPC and LinodeMachine created with CAPL v0.9.x to v1alpha2 LinodeVPC and LinodeMachine reconciled with CAPL v0.10.x.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Special notes for your reviewer:

TODOs:

• squashed commits
• includes documentation
• adds unit tests
• adds or updates e2e tests

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.15%. Comparing base (59420ee) to head (44d2324).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1081   +/-   ##
=======================================
  Coverage   69.15%   69.15%           
=======================================
  Files          71       71           
  Lines        6543     6543           
=======================================
  Hits         4525     4525           
  Misses       1724     1724           
  Partials      294      294           

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