[refactor] Controllerserver (part 2) - createvolume refactor with added test coverage

[komer3]

General:

• Have you removed all sensitive information, including but not limited to access keys and passwords?
• Have you checked to ensure there aren't other open or closed Pull Requests for the same bug/feature/question?

Pull Request Guidelines:

1. Does your submission pass tests?
2. Have you added tests?
3. Are you addressing a single feature in this PR?
4. Are your commits atomic, addressing one change per commit?
5. Are you following the conventions of the language?
6. Have you saved your large formatting changes for a different PR, so we can focus on your work?
7. Have you explained your rationale for why this feature is needed?
8. Have you linked your PR to an open issue

[codecov]

Codecov Report

Attention: Patch coverage is 53.71179% with 106 lines in your changes missing coverage. Please review.

Project coverage is 45.97%. Comparing base (20a6dc1) to head (b2d658a).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
mocks/mock_linodeclient.go	30.43%	96 Missing ⚠️
internal/driver/controllerserver.go	0.00%	8 Missing ⚠️
internal/driver/controllerserver_helper.go	97.59%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #234      +/-   ##
==========================================
+ Coverage   40.13%   45.97%   +5.84%     
==========================================
  Files          26       27       +1     
  Lines        1936     2101     +165     
==========================================
+ Hits          777      966     +189     
+ Misses       1120     1090      -30     
- Partials       39       45       +6     

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