[feat] Add ObjectStorageKey

[bcm820]

What this PR does / why we need it:

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 84.09894% with 45 lines in your changes missing coverage. Please review.

Project coverage is 66.27%. Comparing base (bd77f69) to head (bd2fd79).

Files	Patch %	Lines
controller/linodeobjectstoragekey_controller.go	80.15%	24 Missing and 2 partials ⚠️
cmd/main.go	0.00%	11 Missing ⚠️
api/v1alpha2/linodeobjectstoragekey_types.go	33.33%	4 Missing ⚠️
cloud/scope/object_storage_key.go	95.87%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #426      +/-   ##
==========================================
+ Coverage   64.89%   66.27%   +1.38%     
==========================================
  Files          72       76       +4     
  Lines        3606     3887     +281     
==========================================
+ Hits         2340     2576     +236     
- Misses       1081     1122      +41     
- Partials      185      189       +4     

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