[breaking] Simplify field names for OBJ bucket, fix broken flatcar link in docs

[AshleyDumaine]

What this PR does / why we need it: This simplifies the field name for the OBJ Bucket Secret

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

Attention: Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.

Project coverage is 62.91%. Comparing base (a95ddfa) to head (1ef6e2e).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
cloud/scope/machine.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #750   +/-   ##
=======================================
  Coverage   62.91%   62.91%           
=======================================
  Files          69       69           
  Lines        6671     6671           
=======================================
  Hits         4197     4197           
  Misses       2240     2240           
  Partials      234      234           

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