[feat] add v1alpha2 of linodeMachineTemplate

[eljohnson92]

What this PR does / why we need it:
This PR adds version v1alpha2 of the linodeMachineTemplate resource
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 25.00000% with 30 lines in your changes missing coverage. Please review.

Project coverage is 67.57%. Comparing base (a417bbc) to head (32d64dd).

Files	Patch %	Lines
api/v1alpha1/linodemachinetemplate_conversion.go	27.58%	16 Missing and 5 partials ⚠️
api/v1alpha2/linodemachinetemplate_webhook.go	0.00%	4 Missing ⚠️
cmd/main.go	0.00%	3 Missing ⚠️
api/v1alpha2/linodemachinetemplate_conversion.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #428      +/-   ##
==========================================
- Coverage   68.08%   67.57%   -0.51%     
==========================================
  Files          60       64       +4     
  Lines        3393     3433      +40     
==========================================
+ Hits         2310     2320      +10     
- Misses        946      971      +25     
- Partials      137      142       +5     

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