[improvement] Add env var toggle for gzip compression of cloud-init user data

[AshleyDumaine]

NOTE: Using this toggle requires using OS images with an updated cloud-init version (>24.3.1)

What this PR does / why we need it: This adds support for gzipping the userData before base64 encoding it so we can fit more configuration into cloud-init.

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 19.44444% with 29 lines in your changes missing coverage. Please review.

Project coverage is 64.59%. Comparing base (4a9c8bf) to head (c4b48fa).
Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
controller/linodemachine_controller_helpers.go	23.07%	18 Missing and 2 partials ⚠️
cmd/main.go	0.00%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #531      +/-   ##
==========================================
- Coverage   64.85%   64.59%   -0.27%     
==========================================
  Files          79       79              
  Lines        5663     5689      +26     
==========================================
+ Hits         3673     3675       +2     
- Misses       1717     1740      +23     
- Partials      273      274       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[eljohnson92]

fwiw I think this is still a valid test case, I hope we don't hit it often but userdata can be too large still

[AshleyDumaine]

fair, just need to figure out how to make data that gzips to more than 16kB

[eljohnson92]

maybe we could decrease the limit for the sake of the test to validate a smaller gzip gets rejected? not sure if that would require too much refactoring to handle