refactor(aws): abstract provider-specific boolean parsing

[u-kai]

What does it do ?

This PR introduces a small abstraction for reading provider-specific boolean values
(e.g. "true" / "false") instead of comparing string literals at call sites.

Motivation

This PR is a follow-up to the ongoing AWS alias refactoring discussion.

During review, it was suggested that directly comparing provider-specific string values
(e.g. prop != "true" && prop != "false") is harder to reason about and more error-prone.
Rather than changing the existing approach in-place, this PR isolates the boolean parsing
logic so different approaches can be evaluated side by side.

Note that this PR intentionally does not update the AdjustEndpoints logic in
provider/aws, as that refactor is being handled in a separate, ongoing PR.

More

• Yes, this PR title follows Conventional Commits
• Yes, I added unit tests
• Yes, I updated end user documentation accordingly

[k8s-ci-robot]

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[k8s-ci-robot]

Hi @u-kai. Thanks for your PR.

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[vflaux]

/ok-to-test

[coveralls]

Pull Request Test Coverage Report for Build 20700489134

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 17 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.01%) to 78.812%

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Files with Coverage Reduction	New Missed Lines	%
endpoint.go	17	91.01%

Totals
Change from base Build 20661074501:	0.01%
Covered Lines:	15812
Relevant Lines:	20063

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💛 - Coveralls