Use URL from linodego create response for etcd-backup endpoint

[amold1]

What type of PR is this?
Use URL from linodego create response for etcd-backup endpoint

What this PR does / why we need it:
This will allow us to use the hostname response from creating the Linode OBJ bucket as the endpoint for the etcd-backup-restore

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

[codecov]

Codecov Report

Attention: Patch coverage is 69.23077% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 42.10%. Comparing base (93ee1c0) to head (2b47320).
Report is 3 commits behind head on main.

Files	Patch %	Lines
cloud/scope/object_storage_bucket.go	66.66%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #218      +/-   ##
==========================================
+ Coverage   42.08%   42.10%   +0.02%     
==========================================
  Files          25       25              
  Lines        1371     1375       +4     
==========================================
+ Hits          577      579       +2     
- Misses        781      783       +2     
  Partials       13       13              

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