[improvement] : allow specifying ipv6 slaac public ranges

[rahulait]

What this PR does / why we need it:

This PR implements support for IPv6 SLAAC (Stateless Address Autoconfiguration) configuration for Linode machines by adding two new optional fields to LinodeMachineSpec: EnableSLAAC and IsPublicIPv6. When EnableSLAAC is enabled, instances can automatically configure IPv6 addresses, and IsPublicIPv6 determines whether these addresses are publicly routable.

• Adds EnableSLAAC and IsPublicIPv6 fields to LinodeMachineSpec API
• Refactors IPv6 configuration logic to support both SLAAC and traditional range-based configuration
• Updates interface creation logic to handle SLAAC IPv6 configuration alongside existing range-based approach

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 75.55556% with 11 lines in your changes missing coverage. Please review.

Please upload report for BASE (main@f3b5e58). Learn more about missing BASE report.
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
...nal/controller/linodemachine_controller_helpers.go	75.55%	8 Missing and 3 partials ⚠️

Additional details and impacted files

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  Coverage        ?   63.14%           
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  Files           ?       71           
  Lines           ?     7332           
  Branches        ?        0           
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  Hits            ?     4630           
  Misses          ?     2428           
  Partials        ?      274           

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[Copilot]

Pull Request Overview

This PR implements support for IPv6 SLAAC (Stateless Address Autoconfiguration) configuration for Linode machines by adding a new IPv6CreateOptions struct with three optional fields: EnableSLAAC, EnableRanges, and IsPublicIPv6. The implementation refactors the existing IPv6 configuration logic to support both SLAAC and traditional range-based IPv6 configuration.

• Adds new IPv6Options field to LinodeMachineSpec API with support for SLAAC and range-based IPv6 configuration
• Refactors interface creation logic to handle both SLAAC and traditional IPv6 range configuration
• Updates test cases to validate new IPv6 configuration options and interface expectations

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
api/v1alpha2/linodemachine_types.go	Adds IPv6CreateOptions struct and IPv6Options field to LinodeMachineSpec
internal/controller/linodemachine_controller_helpers.go	Refactors IPv6 configuration logic to support both SLAAC and ranges
internal/controller/linodemachine_controller_helpers_test.go	Updates test validation and adds new test cases for IPv6 configuration
config/crd/bases/infrastructure.cluster.x-k8s.io_linodemachines.yaml	Adds CRD definitions for new IPv6Options fields
config/crd/bases/infrastructure.cluster.x-k8s.io_linodemachinetemplates.yaml	Adds CRD definitions for new IPv6Options fields in machine templates
api/v1alpha2/zz_generated.deepcopy.go	Generated deep copy methods for IPv6CreateOptions
docs/src/reference/out.md	Documents new IPv6CreateOptions API fields

[komer3]

LGTM!